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	$235.80	8.249%	$255.2511	$255.25	$255.25	$255.30
Purchase #2	$222.87	3.605%	$230.9045	$230.90	$230.90	$230.90
Purchase #3	$165.53	4.699%	$173.3083	$173.31	$173.30	$173.30
Purchase #4	$14.53	10.565%	$16.0651	$16.07	$16.05	$16.10
Purchase #5	$54.35	13.518%	$61.697	$61.70	$61.70	$61.70
Purchase #6	$82.76	9.141%	$90.3251	$90.33	$90.35	$90.30
Purchase #7	$192.94	6.638%	$205.7474	$205.75	$205.75	$205.70
7 purchase totals =	$968.78		$1,033.2985	$1,033.31	$1,033.30	$1,033.30