Epos software required for Tea store

Need a ePos software IOS application based front end and back end could be cloud or whatever the choice, it doesn't matter, backend and front should sync in seconds, as soon as changes will be made at the back end A fully customized Tea with different toppings with the choice of different size and different toppings with additional price, I want very simple system where my staff can cock in and clock out, customised button colours so I can change the colours of the each and every button available in the APP. Backend must have bulk upload option of the inventory. There should be categories in the app as well If I want to add any Category.