What some of the chart views on both the NZX & ASB are doing is showing a chart of [normal] trades upto the pre-close at 16:45 but not the result of the closing auction at 17:00.
Thus the price discrepancy.

As an engineer, technical analysis software engineer and web-site creator (click links in signature below) I can tell you these chart implementations are what we in the business call 'a load of rubbish'.

Try http://stocknessmonster.com