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	$243.47	8.590%	$264.3841	$264.38	$264.40	$264.40
Purchase #2	$206.76	7.402%	$222.0644	$222.06	$222.05	$222.10
Purchase #3	$40.90	13.624%	$46.4722	$46.47	$46.45	$46.50
Purchase #4	$10.70	7.462%	$11.4984	$11.50	$11.50	$11.50
Purchase #5	$60.91	8.697%	$66.2073	$66.21	$66.20	$66.20
Purchase #6	$84.29	13.671%	$95.8133	$95.81	$95.80	$95.80
Purchase #7	$148.78	5.161%	$156.4585	$156.46	$156.45	$156.50
7 purchase totals =	$795.81		$862.8982	$862.89	$862.85	$863.00