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	$157.59	4.804%	$165.1606	$165.16	$165.15	$165.20
Purchase #2	$146.52	10.382%	$161.7317	$161.73	$161.75	$161.70
Purchase #3	$223.91	10.566%	$247.5683	$247.57	$247.55	$247.60
Purchase #4	$86.88	3.271%	$89.7218	$89.72	$89.70	$89.70
Purchase #5	$164.48	9.365%	$179.8836	$179.88	$179.90	$179.90
Purchase #6	$45.63	10.835%	$50.574	$50.57	$50.55	$50.60
Purchase #7	$122.30	5.858%	$129.4643	$129.46	$129.45	$129.50
7 purchase totals =	$947.31		$1,024.1043	$1,024.09	$1,024.05	$1,024.20