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	$84.73	12.466%	$95.2924	$95.29	$95.30	$95.30
Purchase #2	$174.30	5.289%	$183.5187	$183.52	$183.50	$183.50
Purchase #3	$199.51	8.397%	$216.2629	$216.26	$216.25	$216.30
Purchase #4	$116.99	13.233%	$132.4713	$132.47	$132.45	$132.50
Purchase #5	$52.57	13.567%	$59.7022	$59.70	$59.70	$59.70
Purchase #6	$38.57	7.254%	$41.3679	$41.37	$41.35	$41.40
Purchase #7	$161.72	4.447%	$168.9117	$168.91	$168.90	$168.90
7 purchase totals =	$828.39		$897.5271	$897.52	$897.45	$897.60