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	$132.84	10.490%	$146.7749	$146.77	$146.75	$146.80
Purchase #2	$225.76	3.456%	$233.5623	$233.56	$233.55	$233.60
Purchase #3	$110.29	8.674%	$119.8566	$119.86	$119.85	$119.90
Purchase #4	$130.95	10.430%	$144.6081	$144.61	$144.60	$144.60
Purchase #5	$114.65	11.109%	$127.3865	$127.39	$127.40	$127.40
Purchase #6	$37.48	10.248%	$41.321	$41.32	$41.30	$41.30
Purchase #7	$46.82	12.141%	$52.5044	$52.50	$52.50	$52.50
7 purchase totals =	$798.79		$866.0138	$866.01	$865.95	$866.10