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	$161.34	6.733%	$172.203	$172.20	$172.20	$172.20
Purchase #2	$206.49	7.760%	$222.5136	$222.51	$222.50	$222.50
Purchase #3	$91.46	9.502%	$100.1505	$100.15	$100.15	$100.20
Purchase #4	$129.62	13.747%	$147.4389	$147.44	$147.45	$147.40
Purchase #5	$11.63	4.607%	$12.1658	$12.17	$12.15	$12.20
Purchase #6	$171.61	8.218%	$185.7129	$185.71	$185.70	$185.70
Purchase #7	$175.57	9.140%	$191.6171	$191.62	$191.60	$191.60
7 purchase totals =	$947.72		$1,031.8018	$1,031.80	$1,031.75	$1,031.80