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	$175.71	13.667%	$199.7243	$199.72	$199.70	$199.70
Purchase #2	$247.27	11.283%	$275.1695	$275.17	$275.15	$275.20
Purchase #3	$112.63	3.679%	$116.7737	$116.77	$116.75	$116.80
Purchase #4	$86.58	3.526%	$89.6328	$89.63	$89.65	$89.60
Purchase #5	$159.30	5.395%	$167.8942	$167.89	$167.90	$167.90
Purchase #6	$95.98	12.682%	$108.1522	$108.15	$108.15	$108.20
Purchase #7	$235.51	8.652%	$255.8863	$255.89	$255.90	$255.90
7 purchase totals =	$1,112.98		$1,213.2330	$1,213.22	$1,213.20	$1,213.30