2 Answers

No, but there is a widespread misconception about duty-free stores. This is essentially what they are: Duty Free shopping exempts an international traveler from having to pay customs duties on various commodities, typically alcohol, tobacco and luxury goods. Since Duty Free items are for consumption or use outside the country, the government doesn't levy taxes on the goods. Because the duties on alcohol and tobacco are typically high wherever you go, shopping for these products Duty Free usually means significant savings. So, if you are leaving the U.S. for example, for another country, you pay no U.S. duty on purchases when you buy and take it with you. If it is brought back to the U.S., then it is subject to customs duties pursuant to the  Harmonized Tariff Schedule of the U.S. Annotated, and applicable taxes, if any.

I personally have never shopped for duty free products online, but my colleague use this web store named Flemingo Diplomatic.