PayPal -- Has an option where you can asses sales tax -- You can even fine tune the sales tax based on zip code -- However, there are certain zip codes that share two counties -- This creates a problem especially, if the sales tax is different. Perhaps you can work with PayPal so that the sales tax is automatically calculated upon the person making an order.
Voting on Ideas
Vote for your favorite ideas by clicking on the up arrow.To undo an upvote, simply click the arrow again. This second click removes your vote.