We buy from sellers not buyers.
Yes, Canadians have a duty-free allowance of $150 on goods imported from the USA and a tax -free allowance of $40.
So if you are in Alberta with only GST applicable, on a $100 USD/$125Cdn purchase, you would pay NO duty but you would pay $6.25 GST.
Plus the service fee from the shipper. Canada Post charges $9.95.
If you are buying from other countries, both the duty-free and the tax-free allowance are only $20Cdn /$15USD.
So if you bought an item for $100 USD /$125Cdn from Brazil, you would pay both duty and tax.