The sales tax on shipping is one thing but ebay has been collecting sales tax on coin and paper money purchases in states that are exempt for over 2 years now. It seems to be a problem that rolls around from state to state and buyer to buyer. Ebay has known about the problem for 2 years and has done nothing to correct it. They are getting free money so why should they stop doing it? They charged me over $60 in sales tax and it took 12 phone calls over 6 months to recover my money. Bottom line, ebay is ripping off buyers in states that don't charge sales tax on coins & paper money.
There are something like 10,000 different taxing jurisdictions in the US, each with different boundaries and rules. Some rules are state-wide, others are city, county, special taxing districts, etc.