You have to use this form: cc:2:0.195
The first value (2) is a costant value ($ 2) the last is the % value, you have to divide by 100 1.95 -> 0.0195.
The script use the higher value.
To add more payment fees use a "," cc:2:0.195,cod:5:0.02
This version calculate taxes on subtotal of the order, I'm working on an improvement to let the script to calculate taxes on the total.