Subtotal in mp_cart_contents_widget shows excl. VAT instead of incl. VAT

Hi there,
my General store settings are "Enter Prices Inclusive of Tax? : YES"
In my shopping cart widget (header or sidebar) though the subtotal shows a price exclusive VAT.

This leaads to a confussion of the customer:
e.g. one product X is in the cart: price EUR 12 (incl. Tax); Taxrate 20%
The cart widget would now show two lines:
product X: Price: EUR 12,00
subtotal: EUR 10,00

I guess a change should be made in "template-functions.php" lines 370-390", but how??