When you register, you can select the country where your card is issued even if you are not in that country now.
When you choose the country, the sales tax (also called VAT or GST in some countries) is automatically calculated and added to the price. If you have two addresses of residence, you can of course choose which tax you would like to pay.
Your country should be the same as the zip code you provide below.
The currency is also automatically converted.