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	$241.32	11.245%	$268.4564	$268.46	$268.45	$268.50
Purchase #2	$41.46	10.634%	$45.8689	$45.87	$45.85	$45.90
Purchase #3	$20.88	6.346%	$22.205	$22.21	$22.20	$22.20
Purchase #4	$195.69	4.651%	$204.7915	$204.79	$204.80	$204.80
Purchase #5	$99.43	9.462%	$108.8381	$108.84	$108.85	$108.80
Purchase #6	$140.65	7.874%	$151.7248	$151.72	$151.70	$151.70
Purchase #7	$177.33	13.142%	$200.6347	$200.63	$200.65	$200.60
7 purchase totals =	$916.76		$1,002.5194	$1,002.52	$1,002.50	$1,002.50