What happens if the internet goes down?
The till keeps working. Sales are queued locally on the device and sync automatically when the connection returns, so a short broadband outage does not stop the counter.
This is designed for the outages a shop actually has — minutes or hours, not days. Queued sales live on that device until they sync, so do not clear the browser data while transactions are still waiting.
Stock levels remain server-authoritative, so once the connection is back the queued sales reconcile against real stock rather than overwriting it.