From Wikipedia:
Towards the end of the 1980s, the 1c and 2c were becoming of little value, and it was decided to withdraw these coins from circulation. The last coins of these denominations were minted for circulation in 1987, with collector coins being made for 1988. The coins were slowly withdrawn from circulation, before finally being demonetised (no longer legal tender) on 1 May 1990.
After the withdrawal of these coins, cash transactions were normally rounded to the nearest 5 cents, a process known as Swedish rounding. Some larger retailers (notably one supermarket chain), in the interests of public relations, elected to round the total price down (so that $4.99 became $4.95 instead of $5.00). Alternatively, many retailers rounded all their prices to the nearest 5 cents to avoid the issue entirely—so a New Zealand shopper often encountered products for sale at prices like $4.95.