[CoLoCo] Cash register?

[Ringo Kamens]

I am running a cafe at my school next year to raise some money for my
smoothie van. Does anybody know of a good program that would run in
Ubuntu and act as a cash register? That way I could keep track of
transactions and stuff. It doesn't have to make receipts, but just
store information so I can see it later. I would appreciate anywhere
you could point me, even if it only does part of what I want.
Comrade Ringo Kamens