Problem with shipping fees

Hi guys,

I have the problem When a customer orders a product from my site the order price doesn’t add up the way it should.

This is what happens:
Subtotal €8,26
Shipping €2,89
Tax €2,34
Total €10,60

When i add the prices together on a calculator the customer should pay 13.49.
Is there a way to solve this problem?

Sincerely,
Mike