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	$96.77	9.448%	$105.9128	$105.91	$105.90	$105.90
Purchase #2	$57.69	4.599%	$60.3432	$60.34	$60.35	$60.30
Purchase #3	$91.32	9.319%	$99.8301	$99.83	$99.85	$99.80
Purchase #4	$14.28	4.619%	$14.9396	$14.94	$14.95	$14.90
Purchase #5	$165.52	5.408%	$174.4713	$174.47	$174.45	$174.50
Purchase #6	$204.52	9.246%	$223.4299	$223.43	$223.45	$223.40
Purchase #7	$21.76	4.536%	$22.747	$22.75	$22.75	$22.70
7 purchase totals =	$651.86		$701.6739	$701.67	$701.70	$701.50