Twitter cash register bot. Direct Message the bot the cost and the paid amount. The bot Direct Messages you your exact change, informs you that you did not pay more than the "item" costs, or ask you to change your formatting. The bots Twitter handle is @CashRegister_Sn. Message me here, on twitter at @amaroney92, or at amaroney92@gmail.com if you would like me to initialize the bot. I don't keep the bot running 24/7.
I made this bot very quickly as a proof of concept. It took about 3 days to make. I don't plan on refactoring this code because was just a proof of concept.