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	$95.50	11.482%	$106.4653	$106.47	$106.45	$106.50
Purchase #2	$194.27	10.513%	$214.6936	$214.69	$214.70	$214.70
Purchase #3	$88.72	12.313%	$99.6441	$99.64	$99.65	$99.60
Purchase #4	$83.94	9.452%	$91.874	$91.87	$91.85	$91.90
Purchase #5	$242.96	4.144%	$253.0283	$253.03	$253.05	$253.00
Purchase #6	$91.50	4.510%	$95.6267	$95.63	$95.65	$95.60
Purchase #7	$37.45	8.537%	$40.6471	$40.65	$40.65	$40.60
7 purchase totals =	$834.34		$901.9791	$901.98	$902.00	$901.90