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	$59.86	6.239%	$63.5947	$63.59	$63.60	$63.60
Purchase #2	$173.67	11.598%	$193.8122	$193.81	$193.80	$193.80
Purchase #3	$71.62	13.795%	$81.5	$81.50	$81.50	$81.50
Purchase #4	$5.42	3.196%	$5.5932	$5.59	$5.60	$5.60
Purchase #5	$233.46	9.346%	$255.2792	$255.28	$255.30	$255.30
Purchase #6	$146.37	13.244%	$165.7552	$165.76	$165.75	$165.80
Purchase #7	$102.85	8.637%	$111.7332	$111.73	$111.75	$111.70
7 purchase totals =	$793.25		$877.2677	$877.26	$877.30	$877.30