Credit cards are used for most purchases in NZ, and are accepted in most hotels and restaurants. ATMs are widely available in cities and larger towns.
Tipping is completely optional in NZ.
Guides Your kayaking guide or tour group leader will happily accept tips; up to $10 is fine.
Restaurants The total on your bill is all you need to pay (though sometimes a service charge is factored in). If you like, reward good service with 5% to 10%.
Taxis If you round up your fare, don't be surprised if the driver hands back your change.