Hi,

The Internet takes tax-free shopping to a new level. In fact, no-tax shopping has become a prime lure of online retailers looking to hook consumers on click-and-charge buying. Despite what you sometimes hear, however, some Internet sales are subject to sales tax, and even when a site doesn't collect sales tax, consumers are technically responsible for remitting any unpaid sales tax on online purchases directly to their state.

I think this article may help you get some more info.
http://www.taxreport.info/document.php?id=34

But to get specific data, its always best to contact your local accountant.

--brookes