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	$196.72	13.753%	$223.7749	$223.77	$223.75	$223.80
Purchase #2	$29.56	11.261%	$32.8888	$32.89	$32.90	$32.90
Purchase #3	$247.99	9.672%	$271.9756	$271.98	$272.00	$272.00
Purchase #4	$84.89	6.867%	$90.7194	$90.72	$90.70	$90.70
Purchase #5	$111.67	4.115%	$116.2652	$116.27	$116.25	$116.30
Purchase #6	$232.43	12.601%	$261.7185	$261.72	$261.70	$261.70
Purchase #7	$234.33	9.244%	$255.9915	$255.99	$256.00	$256.00
7 purchase totals =	$1,137.59		$1,253.3339	$1,253.34	$1,253.30	$1,253.40