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	$87.37	9.605%	$95.7619	$95.76	$95.75	$95.80
Purchase #2	$218.93	7.634%	$235.6431	$235.64	$235.65	$235.60
Purchase #3	$221.54	12.754%	$249.7952	$249.80	$249.80	$249.80
Purchase #4	$218.68	3.278%	$225.8483	$225.85	$225.85	$225.80
Purchase #5	$244.29	4.698%	$255.7667	$255.77	$255.75	$255.80
Purchase #6	$113.57	3.458%	$117.4973	$117.50	$117.50	$117.50
Purchase #7	$89.97	11.487%	$100.3049	$100.30	$100.30	$100.30
7 purchase totals =	$1,194.35		$1,280.6174	$1,280.62	$1,280.60	$1,280.60