I agree with garyhaupt to a degree.
I'm always friendly, with a smile and "how are you". Often not reciprocated, but that's fine, they are doing their job.
However, I always answer the questions directly, to the point, and add no more.
Whether they decide to come into your rig for a lookylook is out of your hands, so I don't worry about it.
When we're done, it's always "you take care" and I'm out of there.
I've never had a significant problem, and I have had the search a couple of times. So be it.
Finally, I prefer to get my cash at an ATM, using a card with no foreign transaction fee added on. I think I get a better rate than inside the bank, but if not, it's a only a few bucks different, and the ATM is a lot quicker. I think it is disrespectful to plan to use US dollars in Canada.