Try your best to relax. I know that's easier said than done but maybe do some breathing exercises or meditation beforehand, drink some herbal tea, take a walk in the park if you can. I think when someone is overly nervous at an interview it shows.

And do you know anything about the grocery store? Like it's history, it's ethics etc? It's always good to show you've done your homework, plus it shows a genuine interest in the job.

Good Luck!