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	$59.68	11.493%	$66.539	$66.54	$66.55	$66.50
Purchase #2	$212.62	5.102%	$223.4679	$223.47	$223.45	$223.50
Purchase #3	$106.70	12.409%	$119.9404	$119.94	$119.95	$119.90
Purchase #4	$233.62	9.232%	$255.1878	$255.19	$255.20	$255.20
Purchase #5	$237.63	5.257%	$250.1222	$250.12	$250.10	$250.10
Purchase #6	$34.29	13.181%	$38.8098	$38.81	$38.80	$38.80
Purchase #7	$60.38	8.747%	$65.6614	$65.66	$65.65	$65.70
7 purchase totals =	$944.92		$1,019.7285	$1,019.73	$1,019.70	$1,019.70