I just talked to Fisto and he asked me if I would like to use his services. I chose maybe later, and when it exited me out of dialogue it gave me 10 caps. I kept doing this and it kept giving me caps. Did this happen to anyone else?

Yes, it is a known bug.

http://fallout.wikia.com/wiki/Fisto

Take a long time to get enough caps to get the Medicine Stick though....