Ask German people!

Try Rossmann or dm rather than a grocery store. Not going to be at the cash register either though, they usually have an aisle for these household goods.

Truthfully they aren't near the register in the US anymore either. They will be in the part of the store where they sell barbecue stuff. If the store sells cigarettes (e.g. liquor store) they will usually have some behind the register and you can sometimes get a matchbook by asking for it. You could also consider a wand lighter, which has a long tube for lighting candles. Those should work for incense and not smoke up the room like matches do.