Mistake in price with tax

[teosweb]

I tried to search other question like me but I don't find, I am sorry to disturb you for this stupid question
I am using V.M 2.0.6 with Joomla 2.5.4
probably the mistake is very stupid
I setted the tax in the section like picture


the calculation in product detail is ok 13 euro (this is the final price that i put in the section of setting article and I flagged the option automatic calculation of base price)


but when I go to final cart the page show me that the calculation of tax has been calculated on Euro 13 instead to show me final price Euro 13


Please help me and sorry for my bad English
http://www.essereobenessere.it/index.php/natura-vita/detersivi-e-detergenti-naturali/noci-per-biobucato-kg-1-detail

ciao
Teosweb