It's a simple question, really. The answer, on the other hand, the real answer I have to give these days, is not what most people want to hear.
I do a lot of my grocery shopping is this funky chain of stores. They used to be nontrivial to find, but nowdays they have stores close to my work, sort of half way between work and home, and not too far from my house. I have yet to see a grumpy employee in any of their stores, and that just seems weird. The optimist in me was of the opinion that maybe they all just like their job, or maybe it was actually a good job, or maybe there were free happy pills in the employee break room. The pessimist mumbled something about aliens and too late, but I was too busy enjoying the sugar-free chocolate they keep supplying to my PCOS-afflicted optimist to listen to her.
Anyway, I used to like chatting with cashiers there-- they are energetic and helpful, and most of them, funny. They always ask how you are without making it obvious that they are only asking because the manager told them to. They tend to look right at you too, and to actually react to whatever you are saying. So... about that...
When I first started venturing out into the world, I found myself unable to tell any of the very nice, cheerful, and well-meaning cashiers that I am actually pretty bad, that my baby died, that I miss him like crazy, and that I wish I didn't have to be there. But I couldn't lie either. So guess what I did? If you guessed I avoided eye contact and tried not to speak, you win an all expense paid trip to the cozy little place I like to call You-don't-want-to-be-here-sville.
I am pretty sure I made some of them uncomfortable. I am also pretty sure some thought I was mean, or a stuck up bitch, or just rude. Some days I didn't even utter a single sound until the "thank you" right at the end as I start pushing my cart away.
The way I know I am better now is that I actually answer. I say "OK." Not much of a conversation starter, but at least I am looking at the cashier when I say it.
I am not so much better, though, that I don't twinge with dread, just a little, as I push my cart toward the registers.