Unless you can modify the bill and coin mechanisms, you are stuck with the power consumption. You can either fit bigger batteries or arrange not to run the mechanisms for a lot of the time.
It is worth checking that the battery is in reasonable condition, and that its voltage has dropped to below 12 V when the mechanisms stop working. If they stop when the voltage is below 12.5 V, then you are not getting the full charge from your battery. Then there are electronic solutions that would increase the life a lot.
Would you be able to fit a timer so the mechanisms are only powered when the shop is open? Could you fit a time switch, like the ones on some corridor lights, so the customers would push the switch to power the mechanisms, put their money in, and then the switch turns itself off a bit later?
Without knowing what the mechanisms do, and how they behave with no power, it is difficult to know what to suggest.