tax question, billing or shipping address? and multiple zones

Hi.

How is tax applied in zencart? Is is applied to the billing address or to the shipping address?

Also, I have an cart which is based in NY. According to the accountants, I should charge both NJ and NY sales tax. That being said, I created 2 tax rates or zones for the tax class "Taxable Goods". NJ is 7% and NY is 8.75%. I did a test order, had the billing address set to NJ and the shipping address to NY. I get a weird output from zencart. At checkout, I am getting charged both NJ and NY sales tax. So for a 38.99 item billed to NJ and shipped to NY, I should either get taxed $2.73 if txaed based on billing address and $3.41 if taxed based on shipping address. However at checkout the tax amount shows as $6.38.

Why am I getting txed for both ny and nj?