Shrug with a confused look is closest when encountering people I do not know. for people you do know and worse work with it is a lot tricker. I was in a position where most coworkers has not influence over me so they got the shrug a few times then later a blunt, thanks - no!

Is it part of life here in the south with an honorable smile.

Why be confrontational when there is no need?

I am a smartass sometimes, so I would probably say, "Are you going to give me cash? That's the only blessing I really need."

I believe its "in style" at least in part due to the success of "scientologist" Moss and her extremely successful TV series Handmaiden.
"Blessed be the fruit"

I hear it all of the time living in the Bible belt so I just smile and shrug it off.

Following:

I've increasing had this 'issue' as well. I'd like to know how to handle it better myself. I must be respected, but so should they.

I"m thinking of countering with, "may the odds be ever in your favor."

I say "So far so good." I do not concern myself with what others say, do, or believe as long as they are not hurting anyone so I'll take those blessings. It is after-all that persons right to freedom of speech and they are wishing you well so why do anything besides kindly accept their gesture. I just don't understand why someone else's beliefs should offend us unless they teach violence (oh that would be the gov.) How can we demand respect but refuse to give it?

I usually just say thanks.

I would've smiled and thanked them. I choose to appreciate their good intention. I like it when people being nice to one another.

First time I heard this was while taking a trip to Austin with my aunt during the womens protests. She was down visiting from Canada and found it baffling. We both eyed each other and nodded. Afterwards we started laughing. We now use it as a inside joke between us whenever we talk in place of saying goodbye. Only recently have I heard it used locally at businesses. But now its become pretty common.

None of the above -- I tell them that's better than a cursed day. Thanks. And walk away.

Religion and work usually doesnt work out well.
So be careful there people can find way to do harm if they find out your a nonbeliever... Only you know you boss so ill leave it at that