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	$153.52	12.184%	$172.2249	$172.22	$172.20	$172.20
Purchase #2	$206.46	7.683%	$222.3223	$222.32	$222.30	$222.30
Purchase #3	$205.30	8.233%	$222.2023	$222.20	$222.20	$222.20
Purchase #4	$37.62	4.438%	$39.2896	$39.29	$39.30	$39.30
Purchase #5	$158.44	13.799%	$180.3031	$180.30	$180.30	$180.30
Purchase #6	$70.55	8.677%	$76.6716	$76.67	$76.65	$76.70
Purchase #7	$146.30	12.814%	$165.0469	$165.05	$165.05	$165.00
7 purchase totals =	$978.19		$1,078.0607	$1,078.05	$1,078.00	$1,078.00