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RFID or Smart Card Cashless Payment System?

Hello!

I was wondering if it was possible to make a cashless (apart from adding funds) payments system.
I was thinking it could be done with an Arduino and RFID reader/writer OR smart card reader/writer.
The balance would be stored on the card (AFAIK data can be stored on the cards) and when the person buying something wanted to add funds to their card, they would hand over money. The person that is staff would type in say 500 for £/$5 and press a button, the user would then scan their RFID tag/card or remove their smart card (because I forgot to mention that they put it in at the beginning) and the funds would be added. If the user then wanted to buy something, they would say what they want, then if the total came to £/$2.50, the staff member would type in 250 and press a different button and the user would scan their RFID tag/card, remove their smart card, etc.

I would just like to know if this is possible.
If you need it explained differently, then just ask!

Thank you!