The bank, which made a profit of $671 million last year, was sued after fraudster Herminia Lanuza's use of its SkyCity branch failed to raise red flags.
Lanuza stole more than $2.7 million from the company she worked for and gambled it away in the high rollers' lounge.
Over a six-year period, she wrote out multiple fraudulent cheques worth $784,363 drawn on the account of her employer, many of which were cashed at the bank's casino branch.
A single cheque for $30,100 was cashed one minute after the bank opened at 9am. Lanuza also took $123,375 from the company's account using withdrawal and transfer slips at the casino branch.
In October 2010 she was sentenced to four years in prison.
She had no authority to carry out the transactions, according to the police summary of facts.
"Many of them were done well after normal business hours and these have to have had a connection with Lanuza's gambling at SkyCity."
BNZ's casino branch is open up to 15 hours a day, seven days a week, and has been labelled "socially questionable" by the Problem Gambling Foundation.
BNZ spokesman Mark Watts said that of 178 bank branches in New Zealand, 46 kept non-traditional hours.
Most of the transactions conducted at the casino branch did not involve casino business.
BNZ SkyCity opening hours:
Monday and Tuesday: 9am-11pm: 14 hours
Wednesday, Thursday and Sunday: 9am-midnight: 15 hours
Friday and Saturday: 9am-12.30am: 15.5 hours
BNZ Queen St opening hours:
Monday to Friday: 9am-4.30pm: 7.5 hours
Saturday and Sunday: Closed