How do you respond to "Have a blessed day"?
"No, thank you! I want to keep my days good instead of blessed."
I always say thank you and you too. I don't really take it as a religious comment-i know that it is, but, I choose to hear "have a great day" when people say that. I have lived in the south for most of my life, and I probably hear that at least once a day.
Once at Aldi the cashier said it and was really taken aback when I responded "No, thank you". I returned a few days later and had the same cashier and she did NOT say it, but gave me a dirty look. This was in a Jewish/Moslem/Hindu neighborhood where Christians were a distinct minority, and I think the manager told her to stop it to avoid potentially offending customers, possibly because of me.