That's my problem, i DON'T WANT TO HAVE A dedicated VLAN for cashless, as it's only for 10 machines max. My question is would the tills see/connect to the main PC whihc could be located on a different VLAN? Some of the tills will be in different VLANs as well.
If you don't want to change your [current] networking setup then don't.
Sometimes, If it ain't Broke, Don't fix it, is really the best advice.
And sometimes it is broke but you don't realize. Why don't you want to have your cashless on a separate vlan? Generally they are horribly insecure, and best isolated (via ACL on your routers) from prying eyes/tools.
They way we do it is to allow the tills and the recharge stations to talk to their DB server and DNS. The management PC exists in the Cashless VLAN with a static IP and the ACLs allows it to operate as a normal machine, but limits incoming packets to those from the servers.