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	$217.70	6.357%	$231.5392	$231.54	$231.55	$231.50
Purchase #2	$10.45	12.499%	$11.7561	$11.76	$11.75	$11.80
Purchase #3	$200.51	9.159%	$218.8747	$218.87	$218.85	$218.90
Purchase #4	$233.83	9.795%	$256.7336	$256.73	$256.75	$256.70
Purchase #5	$113.53	3.195%	$117.1573	$117.16	$117.15	$117.20
Purchase #6	$157.57	4.785%	$165.1097	$165.11	$165.10	$165.10
Purchase #7	$85.83	11.487%	$95.6893	$95.69	$95.70	$95.70
7 purchase totals =	$1,019.42		$1,096.8599	$1,096.86	$1,096.85	$1,096.90