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	$239.72	10.147%	$264.0444	$264.04	$264.05	$264.00
Purchase #2	$194.57	11.324%	$216.6031	$216.60	$216.60	$216.60
Purchase #3	$100.86	5.547%	$106.4547	$106.45	$106.45	$106.50
Purchase #4	$95.58	4.267%	$99.6584	$99.66	$99.65	$99.70
Purchase #5	$102.69	8.530%	$111.4495	$111.45	$111.45	$111.40
Purchase #6	$71.26	13.731%	$81.0447	$81.04	$81.05	$81.00
Purchase #7	$105.98	10.171%	$116.7592	$116.76	$116.75	$116.80
7 purchase totals =	$910.66		$996.0140	$996.00	$996.00	$996.00