It's quit simple, I clear my own products three times a week from Buffalo to Hamilton.
Each day Canada Customs sets the exchange rate for the next day based on the closing rate from the bank of canada. If the items are US or Mexico there is no duty, only gst and/or pst which is calculated on the "exchanged valve" ie $100.00 usd x 1.1537 (todays rate) = $115.37 cdn x GST and/or PST.
Also the freight to get the goods to you is ADDED into the cost of the items BEFORE the exchange or applicable duty is applied.
If you bring in engine parts from Tiawan/Japan?China the duty is 5% (calculated on the landed cdn cost)
Tires from anywhere other than NAFTA zone is 7%.
Etc,etc.
The real killer is the brokerage, UPS and the rest of them are pirates when it comes to brokerage charges.
If you are in the Niagara/Hamilton/Toronto area I can help you out and have it shipped to my address and I'll clear it.
Scott