Yes I do it.

AND when it is hot, as it more often than not is in Perth, I even leave the keys in the car and it running so the air con is on! ***SHOCK HORROR***

And my baby or my car have never been stolen, approached or broken into, nor has my child ever become dehydrated, unconscious or damaged for being alone in a car for 5 minutes! lol

Seriously though, why should you feel bad? How do you think the world would function if every mother had to get her 1, 2, 5 children out of the car for the 2 minutes it takes every time she went to pay for petrol?
Again it is one of those things - bad things CAN happen, DO happen, but the chances of them actually happening to an individual in ordinary circumstances are so minute as to make it ridiculous to cater for every such chance....the petrol station could get held up while you are in there...It could blow up...There could be an earthquake or your car could get struck by lightening...

Then again...it most likely will not.

*shrug* Stand by your choices babe, you are a good mum and you know it.