I.
You could pick one store, go there regularly and build rapport with the cashiers and clerks.
Go at different times to see which type of customer shops when. Bonus point if it’s in A SHOPPING CENTER WITH A GYM or next to a college campus. Then pick the day/time that is best for you to buy groceries+approach.
II.
Go to multiple stores away from your neighborhood where you probably won’t be noticed and practice approaches there.
Make sure you are actually a customer while doing this and not just walking around asking women for their phone number.
You can probably stay as long as you like with just $10.00 in your pocket.
You don’t really need any fancy openers, just keep things light and brief.
Be sure to make eye contact and smile a little, but don’t overdo it. Don’t approach from behind.
When in the meat department: “This place is a real meat market, huh?”
The beer/wine section is also recommended.