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	$37.76	7.119%	$40.4481	$40.45	$40.45	$40.40
Purchase #2	$221.84	11.683%	$247.7576	$247.76	$247.75	$247.80
Purchase #3	$55.31	13.109%	$62.5606	$62.56	$62.55	$62.60
Purchase #4	$38.43	4.647%	$40.2158	$40.22	$40.20	$40.20
Purchase #5	$244.90	12.595%	$275.7452	$275.75	$275.75	$275.70
Purchase #6	$170.55	8.846%	$185.6369	$185.64	$185.65	$185.60
Purchase #7	$40.28	4.203%	$41.973	$41.97	$41.95	$42.00
7 purchase totals =	$809.07		$894.3372	$894.35	$894.30	$894.30