That’s gross using the store’s grinder. Yuk. Yuk. Yuk. Who knows who or what has been touching that thing or how long it has gone without being cleaned.
Use your clean non-germy home food processor.
I actually find that the "germ phobics" are often the sickliest people. I am a believer that you keep your immune system healthy by exposing yourself to germs. Just like a fit runner will fall out of shape quickly if he does not run a certain number of miles a week, so will your immune system. I'm not saying be stupid about it. Obviously you want to maintain a standard of hygiene.
Celebrities like Howard Hughes and Michael Jackson were germ-phobic and they had miserable lives. Remember Michael Jackson walking around with his surgical mask so that he could avoid other people's germs?