Change cart amount

[Chill_user]

Hello guys and ladies,

I like to ask you a stupid question, but very important for me:

How can I modify total of the cart, to add some extra fees? actually this one:

$this->context->cart->getOrderTotal();

I need actually modify or make my own function to rewrite amount final?

Example:

getOrderTotal() = 100$ 

I need modify it to 105$

Please help!

[Chill_user]

Anyone?