Is there anyway to force my site to use the PayPal shopping cart? The controls there to set up shipping methods and sales tax are already built and do what I want.
Not sure if I understand the question correctly but if you need to leave only one payment system - PayPal in eShop you can disabled rest payment systems in main administrator Sitebuilder configuration:
Server -> Modules -> Eshop section.
If you meant something else please give me more details on the question.
Facebook
Twitter