Yes, seems to be partly regulation and enforcement partly cultural in a voluntary code of conduct that tends towards benefit to the consumer. For example,

[All the major grocery retailers] are signatories to the voluntary code of practice for computerised checkout systems in supermarkets. Generally, this means that if an item is scanned at the checkout at a higher price than it says on the shelf or as advertised, a customer is entitled to receive the first item free and all multiples of the same item at the lower price.

https://www.choice.com.au/shopping/consumer-rights-and-advic...

This practice not just matches price (dang, you caught us out this time), but incentivises minimising errors (oops, our bad, have it for free).