Up here, if someone wants to smile and say "Have a nice day", they will do so while making eye contact and you can tell they genuinely mean it. They are usually prompting you for further friendly chit-chat and happiness. Even when there are other customers waiting in line - those customers will be made to wait while two people have a friendly chat.
When they don't want to say "Have a nice day", they won't. Likely they won't say anything at all or kind of grunt/mumble and just move along (even in retail) - but at least you know they're being genuine either way.
Last time I went back to "the real world" I was shocked time and time again when someone would say "Have a nice day" - I'd start to return the sentiment and be utterly disgusted the person wasn't even looking at me, and wasn't even paying attention to me. It all felt so fake, and I was quickly tired of it.
Lots of business up here have a little sign in their shop "Yukon hospitality - it grows on you".
I genuinely wonder if the climate has something to do with this. Extreme cold and very dark days tend to bring people together, and tends to make people more genuine and humble, in my experience.