Steve:

Set it up as a sales tax. If the customer wants to pay by credit card then select the Tax Group "CC - Credit Card" with the first Jurisdiction being "Credit Card Fee". Make the regular Sales Tax the second Jurisdiction.

You will also need to figure out if the credit card fee is subject to sales tax (I believe it will be if the items and/or customer are subject to sales taxes. If so then make the first jurisdiction taxable.

Need help, call me.