Is the extension compatible with 3rd party payment methods?
The extension uses standard Magento features to add its own total.
If the payment method doesn't send information to payment gateway then there shouldn't be any problem.
But if the payment method redirects the customer to a 3rd party server or sends the order total to its own website, then some problems may occur. Often such payment methods don't support additional totals.
If you've encountered such a payment method, contact us — in most cases we will be able to add its support to our extension.