Hello,
The reason for the tax is that the reseller we use (Register Now) does seem to have residency in multiple countries.
If you wish to purchase directly from us via Paypal or personal check, then you will not have to pay any tax.
For more information see the bottom half of this page:
http://reaper.fm/purchase.php
Note that we can't currently accept direct purchases from California residents.. but everywhere else is OK.
-Justin