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	$151.42	7.457%	$162.7114	$162.71	$162.70	$162.70
Purchase #2	$162.77	9.638%	$178.4578	$178.46	$178.45	$178.50
Purchase #3	$95.33	11.741%	$106.5227	$106.52	$106.50	$106.50
Purchase #4	$13.95	4.464%	$14.5727	$14.57	$14.55	$14.60
Purchase #5	$15.63	11.344%	$17.4031	$17.40	$17.40	$17.40
Purchase #6	$99.38	11.107%	$110.4181	$110.42	$110.40	$110.40
Purchase #7	$105.95	5.634%	$111.9192	$111.92	$111.90	$111.90
7 purchase totals =	$644.43		$702.0050	$702.00	$701.90	$702.00