With a 2-0 lead at halftime, Australia ramped up their stranglehold on the game when Whetton added his second shortly after the break after he deflected a drive in to the circle from Aran Zalewski.
New Zealand looked flat for much of the second spell but Steve Edwards provided some much-needed inspiration with a stunning solo effort mid-way through the half.
Their hopes were of a comeback were short-lived through as Russell Ford thundered home Australia's fourth after he received a pass from Simon Orchard.
A penalty corner from Glenn Simpson gave Australia their fifth in the 64th minute as the home crowd of 2300 were silenced.
The Black Sticks had their share of chances during the game but they were disappointing in front of goal and couldn't make the most of their opportunities.
New Zealand, the world No 5, needed to be better against world No 2 Australia and they will rue their missed chances.
Australia's margin of victory would have been a lot greater had it not been for the work of goalkeeper Hamish McGregor, who was agile in the circle throughout the contest.
With a couple of minutes left, Nick Haig added New Zealand's second from a penalty corner but it mattered little.
Earlier in the day, the women's Black Sticks lost their final 5-4 against Australia in a shoot-out. The scores were locked at 2-2 following regulation time and penalties were needed to decide a winner.
In the third-place playoff encounters, Papua New Guinea's men's side beat Samoa 3-0, while the Samoan women beat PNG 4-3 in a shoot-out after they were level at 0-0 following 70 minutes.