Can I specify “no tax” to override paypal’s regional tax default?

I have a paypal account that I use to sell T-shirts and DVDs. Therefore, I have the a default tax (New York State) set up on that account to add tax to all physical items.

I also want to use WordPress Simple Paypal Shopping Cart to sell registrations for educational classes. For those, I DO NOT want to collect sales tax. Is there a shortcode to add to turn off tax for these items? Otherwise, I need to take away tax in the Paypal account, which breaks the checkout for physical items.

-M