You are permitted 200 grams of loose tobacco, plus 200 cigarettes, plus 50 cigars, per adult, after being out of Canada for 72 hours or more, as long as the combined value does not exceed $800.00 CDN.
If ordering online from outside Canada, you may be required to pay Federal Duty, Provincial Taxes, and GST on ANY quantity. Yes, even on a 50 gram tin.
It depends on how "letter of the law" the customs official is as your package clears customs.
I strongly suggest that IF you order online you make sure the sender declares the contents of any package correctly. Declaring tobacco as hobby supplies or pipe filler may bring a smile to your face, but Canada Customs will take a dim view and you and the shipper may end up getting tagged and then each and every package you buy or they ship will get flagged and inspected.
Mike