There are a couple of different modules that will process InternetSecure. The one I have has a field near the bottom that says "Totals to send" and in there I have "ot_tax,ot_shipping" this passes on the tax and shipping variables to InternetSecure.
I have three different modules for InternetSecure and TWO of them have that field. The third does not and does not work.
I'm having trouble passing a discount variable through mine.... it adds in the discount rather than taking it off.
See if that helps!
Missy