Sales tax for online sales is very complicated. Sales tax is charged at the location where the product is delivered, not where the seller is located. Amazon's Marketplace Tax Collection should take care of your sales tax obligations. Below is a link to an FAQ about it that I found on Amazon Seller Central. If you need more information ask Amazon or look in the Seller Forums. There are also third-party tools for handling sales tax for Amazon sellers.
Marketplace Tax Collection FAQ
