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	$162.31	8.343%	$175.8515	$175.85	$175.85	$175.90
Purchase #2	$83.62	6.559%	$89.1046	$89.10	$89.10	$89.10
Purchase #3	$19.66	10.188%	$21.663	$21.66	$21.65	$21.70
Purchase #4	$77.44	8.167%	$83.7645	$83.76	$83.75	$83.80
Purchase #5	$186.75	4.130%	$194.4628	$194.46	$194.45	$194.50
Purchase #6	$223.57	12.145%	$250.7226	$250.72	$250.70	$250.70
Purchase #7	$123.99	13.317%	$140.5017	$140.50	$140.50	$140.50
7 purchase totals =	$877.34		$956.0707	$956.05	$956.00	$956.20