Okay...I like to see everywhere the tax-inclusive prices. So I set the tax amount 19% at the backend, removed the - $ATC_itemPrice += ($ATC_itemPrice * .19);// column binding - at the detail page and added the - ><?php echo WA_eCart_DisplayMoney($eCart1, ($eCart1->GrandTotal() .......($eCart1 = $WA_Store_Cart) in the cart page.
The result is still same.
If you take a look at this item Products_Detail.php?ProductID=8 you can see what is really going on.
Maybe I do something wrong.