diff --git a/pos_payment_method_cashdro_rounding/README_DEV.md b/pos_payment_method_cashdro_rounding/README_DEV.md
new file mode 100644
index 0000000..0c2e5f5
--- /dev/null
+++ b/pos_payment_method_cashdro_rounding/README_DEV.md
@@ -0,0 +1,52 @@
+# pos_payment_method_cashdro_rounding
+
+Sends the CashDro the amount the customer is really expected to pay — the due
+amount with the PoS **cash rounding** applied — instead of the plain due amount
+the OCA module asks for.
+
+## Why
+
+A CashDro can only give change with the coins it holds. When the PoS is
+configured with a cash rounding (`pos.config.cash_rounding`, typically to 0.05
+so that 1 and 2 cent coins are not needed), asking the drawer for the unrounded
+due leaves it trying to return change it does not have.
+
+Core already computes that amount: `PosOrder.getDefaultAmountDueToPayIn()` is
+what a payment line defaults to when it is created. We simply reuse it, so the
+drawer is asked for exactly what the payment screen shows.
+
+`shouldRound()` decides whether the rounding applies at all — it takes
+`only_round_cash_method` into account, and the CashDro method is a cash one, so
+in practice it is always true when a cash rounding is configured.
+
+## How
+
+One single patch on `PaymentCashdro.prototype._cashdro_amount()`, the hook
+`pos_payment_method_cashdro_flow_fix` extracted for this. Everything else of the
+OCA payment flow (request, acknowledge, polling, error handling) is untouched.
+
+Two things this deliberately does **not** do:
+
+- It does not touch the **reversals**. There the amount to send is the one of
+  the line being given back, not the remaining of the order, and it is already
+  the rounded figure that was collected. Rounding it a second time against the
+  order total would ask the drawer to collect the total all over again.
+- It does not touch `_cashdro_payment_url()`, which is what it patched until
+  `18.0.1.1.0`. That method is shared by the payment and the reversal paths,
+  which is exactly how the reversal bug above got in, and it collides with the
+  fix modules that also patch it — the outcome then depending on the asset load
+  order.
+
+## Dependencies
+
+Needs `pos_payment_method_cashdro_flow_fix` for the `_cashdro_amount()` hook,
+and through it `pos_payment_method_cashdro_fix`: without them the OCA module
+does not work on 18.0 at all, so there is nothing to round.
+
+## Testing
+
+There are no automated tests — the flow needs a CashDro answering on the
+network. To check it by hand, configure a cash rounding of 0.05 on the PoS, take
+an order to a total that is not a multiple of 0.05 (e.g. 17.43) and confirm the
+drawer asks for 17.45. See the `USAGE` of
+`pos_payment_method_cashdro_flow_fix` for how to read a failure.
diff --git a/pos_payment_method_cashdro_rounding/__manifest__.py b/pos_payment_method_cashdro_rounding/__manifest__.py
index a16b1e3..1ac11c0 100644
--- a/pos_payment_method_cashdro_rounding/__manifest__.py
+++ b/pos_payment_method_cashdro_rounding/__manifest__.py
@@ -1,18 +1,19 @@
+# Copyright Criptomart
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
 {
     "name": "POS CashDro Rounding",
-    "version": "18.0.1.0.0",
+    "version": "18.0.1.1.0",
     "summary": "Apply cash/currency rounding to CashDro payment request amount.",
     "category": "Point of Sale",
     "license": "AGPL-3",
     "author": "Criptomart",
     "depends": [
-        "point_of_sale",
         "pos_payment_method_cashdro",
+        "pos_payment_method_cashdro_flow_fix",
     ],
     "assets": {
         "point_of_sale._assets_pos": [
             "pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js",
         ],
     },
-    "installable": True,
 }
diff --git a/pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js b/pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js
index eb01842..d369ebc 100644
--- a/pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js
+++ b/pos_payment_method_cashdro_rounding/static/src/js/cashdro_rounding.esm.js
@@ -17,21 +17,29 @@ patch(PaymentCashdro.prototype, {
      * really expected to pay: the due amount with the cash rounding applied,
      * which is the very same amount core defaults a payment line to.
      *
-     * Only the url builder is patched so the rest of the payment flow of the
-     * base module (request, acknowledge, polling and error handling) is kept.
+     * The hook belongs to `pos_payment_method_cashdro_flow_fix`, where the
+     * amount is computed. This module used to patch `_cashdro_payment_url`
+     * instead, which is shared with the reversals: there the amount to send is
+     * the one of the line being given back, not the remaining of the order, so
+     * reversing a paid order asked the drawer to collect the rounded total all
+     * over again.
      */
-    _cashdro_payment_url(parameters) {
-        const order = this.pos.get_order();
-        const line = order.get_selected_paymentline();
-        if (!line || !order.shouldRound(line.payment_method_id)) {
-            return super._cashdro_payment_url(...arguments);
+    _cashdro_amount(line, reversal) {
+        const order = line.pos_order_id;
+        // `shouldRound` and `getDefaultAmountDueToPayIn` came with the 18.0 tax
+        // totals rework. On a build that predates them, fall back instead of
+        // breaking the payment with a TypeError the operator would read as one
+        // more connection error.
+        const rounds =
+            !reversal &&
+            typeof order.getDefaultAmountDueToPayIn === "function" &&
+            order.shouldRound?.(line.payment_method_id);
+        if (!rounds) {
+            return super._cashdro_amount(...arguments);
         }
         // CashDro treats decimals as positions in an integer, so we round the
         // product to avoid the trailing decimals of the floating point
         // computation or the drawer would reject our request.
-        const amount = Math.round(
-            order.getDefaultAmountDueToPayIn(line.payment_method_id) * 100
-        );
-        return super._cashdro_payment_url({ ...parameters, amount });
+        return Math.round(order.getDefaultAmountDueToPayIn(line.payment_method_id) * 100);
     },
 });