We gave this matter serious thought. With so many countries having their own sales, value added, state and consumer taxes, and being in a competitive landscape, we suggest it is best to set a final selling price for your applications globally and have sales taxes deducted where applicable.

Example:
$10 including sales taxes set as final price, selling in x EU country (e.g 17.5% VAT) equates to your actual selling price excluding VAT as $8.51 (formula: $10/1.175)

This sales tax is not related to any income tax or possible withholds from the US tax office.

Related links:
http://en.wikipedia.org/wiki/Taxation_in_the_European_Union

An important part of our offering, is that we handle the sales tax issues on behalf of you (the developer) and there will be no further sales tax declarations required from your side in the US & EU, since we handle the submissions including WA state sales tax & VAT in all EU member states.

Sales Tax Rates
20.00% Austria
21.00% Belgium
20.00% Bulgaria
25.00% Croatia
21.00% Czech Republic
19.00% Cyprus
25.00% Denmark
20.00% Estonia
24.00% Finland
20.00% France
19.00% Germany
24.00% Greece
27.00% Hungary
23.00% Ireland
22.00% Italy
21.00% Latvia
21.00% Lithuania
17.00% Luxembourg
18.00% Malta
21.00% Netherlands
25.00% Norway
23.00% Poland
23.00% Portugal
20.00% Romania
20.00% Slovakia
22.00% Slovenia
21.00% Spain
25.00% Sweden
8.00% Switzerland
20.00% United Kingdom
9.50% WA, USA