You could do all kinds of slip-of-the-hand kinda junk, but the fact is, the border guys open up whatever they want, and the x-rays and other machines they use show what's inside a package with basically perfect clarity.
It's a criminal offense to misdeclare a package, if I'm not mistaken, and while no one is likely to be prosecuted for shipping a half kilo of tobacco marked as tea.... it's not something that's probably a super good idea.
As the other guys have stated, even with taxes etc, both provincial and federal, it's far cheaper to buy tobacco online and have it shipped. You can find the rundown here: http://www.nsra-adnf.ca/cms/index.cfm?group_id=1199
And you can find the actual taxes charge in the tax act online somewhere too. But the long story short is, it's still legal to order from the USA and it's much cheaper to do so under all circumstances.