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	$204.72	8.663%	$222.4549	$222.45	$222.45	$222.50
Purchase #2	$170.28	6.844%	$181.934	$181.93	$181.95	$181.90
Purchase #3	$97.71	3.267%	$100.9022	$100.90	$100.90	$100.90
Purchase #4	$177.32	11.115%	$197.0291	$197.03	$197.05	$197.00
Purchase #5	$201.34	12.594%	$226.6968	$226.70	$226.70	$226.70
Purchase #6	$105.98	5.610%	$111.9255	$111.93	$111.95	$111.90
Purchase #7	$147.74	7.300%	$158.525	$158.53	$158.55	$158.50
7 purchase totals =	$1,105.09		$1,199.4675	$1,199.47	$1,199.55	$1,199.40