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	$106.89	7.743%	$115.1665	$115.17	$115.15	$115.20
Purchase #2	$79.55	12.594%	$89.5685	$89.57	$89.55	$89.60
Purchase #3	$93.81	7.120%	$100.4893	$100.49	$100.50	$100.50
Purchase #4	$225.92	4.801%	$236.7664	$236.77	$236.75	$236.80
Purchase #5	$54.42	9.790%	$59.7477	$59.75	$59.75	$59.70
Purchase #6	$218.87	13.174%	$247.7039	$247.70	$247.70	$247.70
Purchase #7	$127.48	7.780%	$137.3979	$137.40	$137.40	$137.40
7 purchase totals =	$906.94		$986.8402	$986.85	$986.80	$986.90