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	$165.63	6.815%	$176.9177	$176.92	$176.90	$176.90
Purchase #2	$216.74	5.533%	$228.7322	$228.73	$228.75	$228.70
Purchase #3	$76.57	8.564%	$83.1275	$83.13	$83.15	$83.10
Purchase #4	$11.94	10.680%	$13.2152	$13.22	$13.20	$13.20
Purchase #5	$121.80	4.718%	$127.5465	$127.55	$127.55	$127.50
Purchase #6	$195.45	13.308%	$221.4605	$221.46	$221.45	$221.50
Purchase #7	$84.50	13.152%	$95.6134	$95.61	$95.60	$95.60
7 purchase totals =	$872.63		$946.6130	$946.62	$946.60	$946.50