To wear or not to wear a helmet .

I have a hiboys2 , rather than getting a ticket for my light being out in my car I’m considering using it more often for errands . To get to the store and back should I wear a helmet? I usually don’t go over 12mph and the highest speed is 19 mph I believe. Should I invest in a helmet? Should it just be a regular helmet, as I’m only going to go about to stores etc .