“Payment Methods Fee / Discount” is an Order Total Extension that helps you setup discounts or extra fees based on the payment method that the customer selects in checkout.
You can setup multiple rules in the extension’s settings. In each rule you can select if it is a discount or a charge, use either fixed or percentage type and apply restrictions based on store (in a multi store installation) and order amount.
Each rule can be named differently in order to show different text to customer.
Multi languages supported as well.
The calculation of a percentage fee or discount depends on the sort order you will set in the extension. So, it will apply to the amounts that appear in the cart totals prior to the discount/fee total row.
For example, if you want to apply the discount/fee only on the subtotal, then you need to place it after the subtotal. If you want to apply to include shipping before apply the discount/fee, then you need to place it after the shipping, etc.