Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$186.32	3.160%	$192.2077	$192.21	$192.20	$192.20
Purchase #2	$45.77	12.173%	$51.3416	$51.34	$51.35	$51.30
Purchase #3	$136.46	11.267%	$151.8349	$151.83	$151.85	$151.80
Purchase #4	$164.26	12.171%	$184.2521	$184.25	$184.25	$184.30
Purchase #5	$146.37	3.138%	$150.9631	$150.96	$150.95	$151.00
Purchase #6	$48.32	4.524%	$50.506	$50.51	$50.50	$50.50
Purchase #7	$247.35	12.440%	$278.1203	$278.12	$278.10	$278.10
7 purchase totals =	$974.85		$1,059.2257	$1,059.22	$1,059.20	$1,059.20