I tied a dog once outside a store to the garbage dumpster. But when you tie them, they can act like they are guarding whatever you tie them to. And, if someone comes up, they may just see the dog and think they should go and pet it and pick on it, etc. On that side of the store, I couldn't see, so I just never did that again. I will only stop at a store and put the dog on a down-stay in front of the windows, run in, grab a hot dog (for the dog), pay and get back out within a minute, keeping the dog in view the entire time.
And even then, it's hard. Because if someone drives up, they may be intimidated by the dog. So I just avoid it like the plague. Once in a blue moon I will do that, and only with the dogs that are totally trained, etc.
Now, when I was a kid, and had our shepherd mix, princess, I would snap her chain off, and we would go for a walk all through the town. She would go onto people's porches and eat their cat food. I would pretend I didn't know her. We would stop at that same store, though it was called Lawson's back then, and now it is called Circle K. Whatever. She would wait for me to buy a day-old chocolate donut. and when I would come out, I would feed it to her.
That dog lived to almost 15, and was healthy as a horse, after surviving stomach cancer shortly after we got her. The vet would examine her year after year expecting that cancer to come back as it was an aggressive form. But it didn't. The old girl never had any other problems. And hundred of chocolate donuts, and a couple of dozen chocolate chip cookies in one go, didn't seem to make any difference.
And she would go down and wait for me to come out of the store, not tied, not trained, not on a stay.