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	$151.72	13.765%	$172.6043	$172.60	$172.60	$172.60
Purchase #2	$227.45	11.273%	$253.0904	$253.09	$253.10	$253.10
Purchase #3	$165.72	4.788%	$173.6547	$173.65	$173.65	$173.70
Purchase #4	$147.90	8.756%	$160.8501	$160.85	$160.85	$160.90
Purchase #5	$202.85	10.811%	$224.7801	$224.78	$224.80	$224.80
Purchase #6	$147.96	9.416%	$161.8919	$161.89	$161.90	$161.90
Purchase #7	$51.25	3.748%	$53.1709	$53.17	$53.15	$53.20
7 purchase totals =	$1,094.85		$1,200.0424	$1,200.03	$1,200.05	$1,200.20