TAX wrong calculations differences: ticket-screen

Hi guys,

Still using v3 (will move to v5 when it's out) because of languages.

Seems that I have a problem setting TAX as it's giving me wrong calculations. I create a tax template with Account Tr.Type=Sale Transaction, Rate 18 (and add Mapping). Then under Ticket Type List I click on Tax Included. I gives me wrong amounts. For example:

a product of 16.99 the taxes appear 2.59 and not the correct 3.06. Then another wired issue: on the ticket it appear subtotal normal, the taxes are ok (3.06) and it's adding the taxes to the total even I click on TAX Included. I attach some pics, might some help.

I also try with

I am doing something wrong??