Ticks below the minimum
Like in the US, more flexibility is extended to hidden orders.
Australia has taken an aggressive approach to hidden orders in the direction of lower ticks.
Aussies have a rich financial that evolved differently than the Dutch custom more familiarly known in the UK and US.
They, like Chicago evolved out of commodities trade rather than trade. When commodities are worth nearly nothing per unit, larger precision comes naturally.
For the Dutch, it was the opposite. A single ship would trade in 1/64 share or for the largest vessels, 1/128 share. Here, there's no point to high precision. New York, founded by the Dutch specialized in logistics just the same.
To a man with a hammer, everything looks like a nail, so both Chicago, Australia, and other financial systems built by commodities rather than trade have extended the higher precision logic to everything else, and pricing is fantastic.
It should not be a surprise why Australia has taken a lead in pushing infinite precision.