The Canadian sales taxes I referred to are what is known as consumption taxes. They get passed on to the end purchaser. There are two of them: one federal applied in all provinces, and the other provincial (state). The provincial tax varies from 0 in Alberta to 9.5% in Quebec. In Quebec they add up to 15%.
A purchaser can avoid paying them if the item purchased is for resale in one manner or another, and if he is registered federally and provincially. As you suspect they do not apply to items "exported" however in this case the "exporter" is going to have to jump through hoops, forms and other paperwork that the normal Subi dealer never encounters in order to not charge the taxes.
Sometimes the purchaser, from outside Canada, can recuperate the taxes already paid by filing a claim somewhere, however you do have to have complete documentation, and I do not know how that is done.
Tariffs concern the importing country so you will have to sort that out on your end. There is a free trade agreement between the US and Can as well as free trade in automobile stuff between the countries. In addition this product must be made in the US so I doubt if any tariff applies. The problem is not the tariff, it is the handling of the item. In Canada I can get stuck with a fee for opening a file even when no tariff is charged. This filing or handling fee ranges from 5$ if it is through Canada Post to infinity if it is through your friendly UPS "service". Shipping by UPS is prohibitive as they charge fees on fees to suck everything they can out of your pockets. They have your stuff so you have to pay up if you want it. I hate UPS. I see no reason for them to treat you differently from me. They will screw you.
Have a good day!