Breakage is calculated on what is called the $1 unbroken price, which is the raw odds from the pools plus 1
they call it Profit per Dollar plus, (also called decimal odds) The breaks are as follows:
Unbroken Price
1.05 to 4.99..... 0.05
5 to 24.99...... 0.10
25 to 249.99..... 0.25
250 and up...... 0.50
this results in the broken price, from which payouts are calculated, and odds posted.To get the full breakage applied to a $2 payout the actual breaks should be multiplied by 2
The Association of Racing Commissioners International provide the model rules from which individual states adapt to their purposes.The calculations are on page 59 of the latest rules.
https://arci.com/model-rules-standards/