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	$207.45	3.874%	$215.4866	$215.49	$215.50	$215.50
Purchase #2	$129.25	6.193%	$137.2545	$137.25	$137.25	$137.30
Purchase #3	$50.26	4.215%	$52.3785	$52.38	$52.40	$52.40
Purchase #4	$95.48	13.643%	$108.5063	$108.51	$108.50	$108.50
Purchase #5	$40.81	6.340%	$43.3974	$43.40	$43.40	$43.40
Purchase #6	$134.45	11.577%	$150.0153	$150.02	$150.00	$150.00
Purchase #7	$43.98	10.177%	$48.4558	$48.46	$48.45	$48.50
7 purchase totals =	$701.68		$755.4944	$755.51	$755.50	$755.60