In New Zealand, we generally thank the driver.
When I leave from the back door, I lightly call, “Thank you.”
Leaving from the front door, I lightly say, “Cheers.”
I live in a small city, so the drivers and I sometimes recognise each other, and they may even know where I am going.
I do this thanks/cheers for both local buses, and for intercity buses.
This habit might be waived if there is a big crowd getting on or off.
This is normal in Palmy and Welly, and probably the rest of New Zealand.