We need to follow NZ's lead and ditch the five cent coin next. Even 10c pieces are a waste of time. Can't think of many cash transactions in my daily life where it would bother me to round to the nearest 20c. Certainly not dinner or a round of drinks, lunch, a full bag of groceries, etc.
There are several thousand, if not million of Australians that would disagree. The ability to round prices by ten or twenty cents at a time is a luxury that cannot be afforded by everyone.
What? If you remove coins and round to the nearest payable amount, it evens out over time. Sometimes you'll pay less than the actual total, sometimes you'll pay more. Prices aren't magically going to increase, so how is this a luxury?
If I ran a large business, I would certainly look at the most-common purchases and combinations of purchases (especially low-cost items, like a candy bar) and consider tweaking prices so I gained rather than lost two pennies on my most common transactions.
Places with limited and standardized menus, like fast-food restaurants, could do this quite easily.
Enough businesses do this, and things no longer even out over time.
To the point where the less-privileged suffer significantly? It's not as though rounding up a bit is going to be the only way businesses try to squeeze out more money.