Thanks, Mihai.
My settings are as follows, though I've tried changing them several times with no improvement:
-Product prices are tax exclusive
-Add per product tax rate to percentage if product has a specific tax rate [none of my products do have different tax rates]
-Apply tax when shipping country is the same as tax rate
I have one tax rate set up, for North Carolina sales in the U.S. at 7.5%, not applied to shipping.
WP E-Commerce calculates tax in the cart correctly, but it doesn't transfer to Paypal for some reason. This problem only seems to have occurred recently--I just caught it the other day, but I believe it began a couple of weeks ago when I updated to the most recent version of WP.
I found an awkward workaround by removing the billing details fields entirely from checkout in Store Settings--since we only accept Paypal payments, that does suffice for the site--and for some reason, tax calculations are now passing on to Paypal. However, this is far from an ideal solution, as we're planning soon on accepting credit card payments directly, and we'll require billing details.
Any ideas what's going on? Thanks very much for your help!
- Brendan