OK, now you just changed the game be telling us you will carry your new little friend in your pocket while working at a gas station. That tells me you are not just looking for something to stop some thug who is harassing you with a club or shank, but your probabilities have risen where you could be facing an armed robbery situation where you life is on the line.

In this case I would carry the biggest gun you can handle efficiently period. That would not be a .380 in my opinion. Although I would recommend one of your Glocks or M&Ps, if they are out of the question I would carry a J Frame of your choice loaded with Speer 135 gr SB +Ps at a minimum. With that said, I would also recommend a lot of practice at multiple targets. You have to be really good with only five shots. Maybe you should reconsider that fine M&P 9C tucked in your waistband.