Hi
If you'll look on $cart object in plgVmConfirmedOrder method you'll see that every tax_id element is zero, although in $method objects for every plugin tax_id is correct.
This happens because in /administrator/components/com_virtuemart/plugins/vmpsplugin.php::onSelectedCalculatePrice zero assigned to $cart_prices[$this->_psType . "_tax_id"]
It should be $cart_prices[$this->_psType . "_tax_id"] = $method->tax_id;
Plus following bug http://forum.virtuemart.net/index.php?topic=98423.0 that VM developers are successfully ignoring.
up