This contribute MultiPaymentFee as opencart plugin to extend the opencart avaibility to include payment fee in order to minimize the merchant lost. The module is helping to offset the transaction fee incur to the payment gateway.
A = (B + C) / 1 - (D / 100)
1) Unzip and upload the contents to the root directory of your OpenCart installation
2) Logon to administrator page, goto 'Admin->Users->User Groups->Edit the Top Administrator'.Then find and check the total/multi_payment_fee for both modify and access. Save.
3) Logon to administrator page, goto 'Extensions ->Order Totals -> Multi Payment Fee'.
4) Install the module, and click edit to configure.
5) Adjust the Sort Order before the Total.Save.