As a rule of thumb, sales tax of any kind doesn't apply when you eport something, but it's not as simple as all that. Firstly, you need to find a company that has the facilities to export and deduct tax from the amount you pay and then, by law, you're supposed to declare your purchase to the inland revenue (or whoever) and pay your local sales tax (in my case, VAT) when you receive the goods.

Sucks, doesn't it. Although I do think that there's a lower limit, below which you are tax exempt on personal imports