improve cash-in error handling

lib/plugins.js

@@ -509,6 +509,20 @@ function plugins (settings, deviceId) {
     .catch(err => logger.error(err))
   }
 
+  function updateCassettes (tx) {
+    // Note: This is the only place we update config from outside admin,
+    // so should be safe even though it's not an atomic operation.
+    //
+    // However, we should make all config changes atomic in the future.
+    const config = configManager.machineScoped(deviceId, settings.config)
+    config.topCashOutDenomination -= tx.bills[0].actualDispense +
+      tx.bills[0].rejected
+    config.bottomCashOutDenomination -= tx.bills[1].actualDispense +
+      tx.bills[1].rejected
+
+    // save
+  }
+
   return {
     pollQueries,
     sendCoins,
@@ -525,6 +539,7 @@ function plugins (settings, deviceId) {
     sendMessage,
     checkBalances,
     buildCartridges,
+    updateCassettes,
     buy,
     sell
   }