Johnny:
Then you need to set up your Invoice specification to print the product sold, GST & PST, Subtotal, Fee (which would be another tax and taxes can be controlled at the customer level, not the terms), and then the grand total. The problem with this is you will not be charging SGT on the fee as you should. My recommendation would be to print the product sold, subtotal, Fee, GST & PST, Total
Exactly how to set all of this up is beyond what this forum can do for you. If you need assistance your Adagio Consultant can help you.