Siri's location-based reminders are great for remembering items when you get home. Adding places you frequently visit into contacts helps Siri create better reminders.
Within your Contacts, add the name of the store in the Company field and put in the address. If the store has more than one location, put a modifier in the Company field to help differentiate such as "Coles Elsternwick".
Once the name is in there, you can tell Siri "Remind me to buy olive oil when I get to Coles Elsternwick." When you arrive at that Coles, Siri will pop up your reminder.