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	$210.61	8.389%	$228.2781	$228.28	$228.30	$228.30
Purchase #2	$247.84	3.570%	$256.6879	$256.69	$256.70	$256.70
Purchase #3	$184.76	6.335%	$196.4645	$196.46	$196.45	$196.50
Purchase #4	$41.95	10.730%	$46.4512	$46.45	$46.45	$46.50
Purchase #5	$207.65	12.455%	$233.5128	$233.51	$233.50	$233.50
Purchase #6	$208.29	10.760%	$230.702	$230.70	$230.70	$230.70
Purchase #7	$67.68	13.415%	$76.7593	$76.76	$76.75	$76.80
7 purchase totals =	$1,168.78		$1,268.8558	$1,268.85	$1,268.85	$1,269.00