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	$94.69	6.149%	$100.5125	$100.51	$100.50	$100.50
Purchase #2	$179.73	8.531%	$195.0628	$195.06	$195.05	$195.10
Purchase #3	$247.97	11.559%	$276.6329	$276.63	$276.65	$276.60
Purchase #4	$142.33	3.746%	$147.6617	$147.66	$147.65	$147.70
Purchase #5	$15.87	8.837%	$17.2724	$17.27	$17.25	$17.30
Purchase #6	$84.72	5.600%	$89.4643	$89.46	$89.45	$89.50
Purchase #7	$143.42	10.523%	$158.5121	$158.51	$158.50	$158.50
7 purchase totals =	$908.73		$985.1187	$985.10	$985.05	$985.20