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	$220.77	11.456%	$246.0614	$246.06	$246.05	$246.10
Purchase #2	$128.41	7.298%	$137.7814	$137.78	$137.80	$137.80
Purchase #3	$60.37	10.208%	$66.5326	$66.53	$66.55	$66.50
Purchase #4	$87.88	3.225%	$90.7141	$90.71	$90.70	$90.70
Purchase #5	$229.85	4.281%	$239.6899	$239.69	$239.70	$239.70
Purchase #6	$188.49	6.504%	$200.7494	$200.75	$200.75	$200.70
Purchase #7	$94.37	11.828%	$105.5321	$105.53	$105.55	$105.50
7 purchase totals =	$1,010.14		$1,087.0609	$1,087.05	$1,087.10	$1,087.00