I've been there before numerous times. Sometimes if I'm really struggling I just say a different name that's easier for me to say, but that feels like a cop out. I doubt the cashier was trying to make you feel bad intentionally, but I know that it's hard to just laugh that stuff off. I remember once reading some kind of study that indicated people listening to stutterers tend to feel MORE uncomfortable than the people actually doing the stuttering. A lot of people just don't know how to react it because they don't come across it very often. It wasn't until I was 17 when I met a fellow stutterer. I think the best thing people can do is just learn to be patient with us.