Collecting sales tax on Internet sales is like trying to gather up all the planet’s sand with a colander.
I'm not sure how it works but at least my state (Michigan) was able to obtain the sales records from an out of state internet tobacco outlet (Dirtcheapcigs.com). Armed with those records, the state treasury went after the buyers demanding all the applicable taxes. And if such taxes were not paid by a certain date, they promptly sent penalty notices equaling %100 of the alleged taxes due...........
That's absurd. Local governments collect tax on nearly all sales across a store counter. and those are still the vast majority of all retail sales. Every major supermarket chain has systems that can track the whole patchwork of sales taxes for all of the stores it runs. K-mart, Sears, Walmart, Blockbuster, Starbucks don't seem to have a lot of difficulty collecting sales tax and making sure it's handed over to the right officials.
It might be difficult, impossible, or not worth the effortto try to track virtual sales, like downloaded software or music (or, of course, porn), but for any physical gods, you've got both a delivery address and almost always a credit card billing address. Pick one and assess the tax there. Set up a geographic database of sales tax rates by address -- I'd be surprised if one didn't already exist.
or herd cats