I renewed my Minnesota Permit to Carry 3 years ago. At that time, I recall from the training that castle doctrine is not in effect in the state, so it's your legal responsibility to retreat if such an option is available.
1. Protecting property
In your workplace, defending property, particularly someone else's property, is not worth it. There may be special circumstances for security guards (if that's what you're employed as), but I'm not familiar with those.
2. Protecting self
Here's a question you should be thinking of during a situation when you can't retreat safely:
"Mr. Bad Guy, are you just here to steal stuff, or are you here to steal stuff and viciously murder any potential witnesses?"
Tough question to answer, but perhaps you can glean the answer from the demeanor of the perpetrator/s, whether he/she is wearing a mask, if there's a High Definition camera, if there are many people (potential witnesses) in the store, etc., etc., etc.
If you are in fear for your life and well-being, with no other way out, worry about the legalities later.
Also get training beyond the minimum required for Minnesota Permit to Carry.
3. Protecting others
My MN instructor stressed his personal policy: "If it ain't kin, I ain't in," meaning that if the situation involves defending someone else other than his own family, he would not get involved. He cited several reasons which made sense.
This is a moral issue you'll have to decide on your own.