Staples should have informed you that brokerage and tax charges are not in the shipping charges. UPS does not know what the destination countries customs will put on each package. Just guessing that this is what you are referring to.
First of all, brokerage charges are covered in the shipping cost. Secondly, there are no taxes on international shipments, they are called custom's duties. And, since Canada is part of NAFTA it is unlikely there would be a duty involved.