Adding additional costs to the cart value

[Bayersk Ølimport]

Hi there,

I'm considering switching to Prestashop. I run a beverage store and I need to know that it's possible to add additional charges (bottle deposits) to the cart value, besides shipping charges.

The idea is: The customer pays X for every product + Y for every 20th product. The final cart value will then be a sum of the initial cart value, shipping charges and the additional costs (X+Y).
And, of course, this has to be transparent to the customer.

Can it be done? Any help would really be appreciated.