Formula for WA which implements the following from this website:

https://www.finance.wa.gov.au/cms/State_Revenue/Duties/Rates/Rates_of_Duty.aspx

Vehicle licence duty – Vehicle mass less than 4.5 tonne

$           0 – $25,000	2.75% of dutiable value (DV)
$  25,001 – $50,000	[2.75 + (DV - 25,000)] % (rounded to 2 decimal places) of dutiable value 6,666.66
$  50,000 and upwards	6.5% of dutiable value

Formula in C9 is:

int({DutyValue}*case({DutyValue},x<=25000,275,x>=50000,650,275+int((x-25000)/66.6666+0.5))/500)/20