Calculating U.S. Taxes (regional)

Hello everyone! I'm looking for some resources that helps you calculate regional taxes. If you have any leads,then please let me know. I'm writing an e-commerce application that will charge users different tax fees, based on where they are located. I hope to find a script that already does that or gain access to an online service that maintains this type of data. I'm open to solutions with the following technologies: PHP SOAP XML or a general Value/Pair response. Any help would be greatly appreciated. Thanks in advance! -john =P e p i e D e s i g n s www.pepiedesigns.com Providing Solutions That Increase Productivity Web Developement. Database. Hosting. Multimedia.