Europeans generally don't tip seawolf although they will often round up a bill. Brits are notorious for not tipping. So they don't encounter an issue when it comes to not having any small bills to offer as a tip.
Nor is the OP going to Europe. The question is about Halifax. Rather than getting excited about my suggesting $1 US bills make no sense, try considering where you would give anyone a $1 tip in Halifax. Valet parking is a primarily a US thing, not often found in Canada. Bellboys have gone the way of the Dodo thanks to Bernard Sadow. Can anyone name a hotel in Halifax that still has bellboys? Some hotels offer valet parking in Halifax but when they do, it is part of the hotel bill, there is no need to tip the valet separately. Typical is self-park $20 and valet park $27 at the Westin. So you pay a $7 'tip' for valet parking.
So the suggestion of taking some $1 US bills makes no sense to me. Whether someone feels they have been insulted by my saying that is not my problem. A $1 US bill in Halifax will be of no use whatsoever as far as I am concerned. I find the idea ridiculous. That does not mean I am saying anything about the person suggesting it, I am attacking the idea, not the person. Some people seem to have difficulty understanding the difference between the two.