You should be taxing buyers from the country you live in.
If you sell to somone form another country there is no tax but the buyer may have to pay import duty. If customs detect it
but thats the buyers problem
Normaly (in the UK anyway) you have to make a fair ammount of sales (about £40,000 I think) before you have to register for VAT.
Beware of using PayPal (i dunno it may work better in the USA) in the UK it's realy bad at approving credit cards and you cannot tell the crooks from the genuine customers half the time! Also PayPal charge you a charge back fee of about £7 for every bad chageback!
I tried to run a business though paypal once it's a nightmare :/
Other people i've talked to say the use an electonic copy of the electrol register to prove somone lives where they say they are instead.
http://www.KumKie.com http://bulldog.servegame.com