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	$54.90	8.223%	$59.4144	$59.41	$59.40	$59.40
Purchase #2	$231.34	9.649%	$253.662	$253.66	$253.65	$253.70
Purchase #3	$196.62	10.676%	$217.6112	$217.61	$217.60	$217.60
Purchase #4	$60.32	6.154%	$64.0321	$64.03	$64.05	$64.00
Purchase #5	$212.89	4.181%	$221.7909	$221.79	$221.80	$221.80
Purchase #6	$104.71	8.141%	$113.2344	$113.23	$113.25	$113.20
Purchase #7	$48.85	13.647%	$55.5166	$55.52	$55.50	$55.50
7 purchase totals =	$909.63		$985.2616	$985.25	$985.25	$985.20