New Zealand is a relatively safe place to carry reasonable amounts of cash and currency is easy to exchange. Otherwise most travellers will have no problems using major credit cards as they are commonly accepted for transactions in most places.
Tipping is becoming more widespread in New Zealand, principally in the major centres where there's been more foreign influence. However, it's certainly not expected in any restaurant. You should tip 5-10% of the bill in a restaurant (not in a simple café) if you feel you have received exceptional service.
New Zealand's banknotes all feature eminent people from the country's history and come in denominations of 5, 10, 20, 50 and 100 dollars.
The New Zealand dollar is made up of 100 cents - there are coins in denominations of 10, 20 and 50 cents and 1 and 2 dollars the coins all featuring various emblems, flora and fauna.