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	$113.73	13.191%	$128.7321	$128.73	$128.75	$128.70
Purchase #2	$40.51	11.307%	$45.0905	$45.09	$45.10	$45.10
Purchase #3	$247.45	11.713%	$276.4338	$276.43	$276.45	$276.40
Purchase #4	$224.37	12.696%	$252.856	$252.86	$252.85	$252.90
Purchase #5	$71.62	8.693%	$77.8459	$77.85	$77.85	$77.80
Purchase #6	$191.59	4.169%	$199.5774	$199.58	$199.60	$199.60
Purchase #7	$111.65	4.441%	$116.6084	$116.61	$116.60	$116.60
7 purchase totals =	$1,000.92		$1,097.1441	$1,097.15	$1,097.20	$1,097.10