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	$66.34	9.458%	$72.6144	$72.61	$72.60	$72.60
Purchase #2	$196.28	3.726%	$203.5934	$203.59	$203.60	$203.60
Purchase #3	$113.75	10.336%	$125.5072	$125.51	$125.50	$125.50
Purchase #4	$57.44	5.689%	$60.7078	$60.71	$60.70	$60.70
Purchase #5	$65.89	5.406%	$69.452	$69.45	$69.45	$69.50
Purchase #6	$244.29	4.869%	$256.1845	$256.18	$256.20	$256.20
Purchase #7	$57.87	3.260%	$59.7566	$59.76	$59.75	$59.80
7 purchase totals =	$801.86		$847.8159	$847.81	$847.80	$847.90