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	$48.53	13.619%	$55.1393	$55.14	$55.15	$55.10
Purchase #2	$212.89	4.823%	$223.1577	$223.16	$223.15	$223.20
Purchase #3	$126.48	11.242%	$140.6989	$140.70	$140.70	$140.70
Purchase #4	$141.38	11.868%	$158.159	$158.16	$158.15	$158.20
Purchase #5	$33.65	9.265%	$36.7677	$36.77	$36.75	$36.80
Purchase #6	$211.69	5.105%	$222.4968	$222.50	$222.50	$222.50
Purchase #7	$223.69	8.658%	$243.0571	$243.06	$243.05	$243.10
7 purchase totals =	$998.31		$1,079.4765	$1,079.49	$1,079.45	$1,079.60