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	$147.45	9.594%	$161.5964	$161.60	$161.60	$161.60
Purchase #2	$63.57	4.680%	$66.5451	$66.55	$66.55	$66.50
Purchase #3	$144.58	9.639%	$158.5161	$158.52	$158.50	$158.50
Purchase #4	$24.77	12.480%	$27.8613	$27.86	$27.85	$27.90
Purchase #5	$158.69	5.628%	$167.6211	$167.62	$167.60	$167.60
Purchase #6	$231.80	9.343%	$253.4571	$253.46	$253.45	$253.50
Purchase #7	$84.28	13.829%	$95.9351	$95.94	$95.95	$95.90
7 purchase totals =	$855.14		$931.5322	$931.55	$931.50	$931.50