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	$105.60	5.523%	$111.4323	$111.43	$111.45	$111.40
Purchase #2	$48.84	10.637%	$54.0351	$54.04	$54.05	$54.00
Purchase #3	$222.44	8.389%	$241.1005	$241.10	$241.10	$241.10
Purchase #4	$30.81	13.492%	$34.9669	$34.97	$34.95	$35.00
Purchase #5	$106.44	7.598%	$114.5273	$114.53	$114.55	$114.50
Purchase #6	$190.52	4.640%	$199.3601	$199.36	$199.35	$199.40
Purchase #7	$43.78	10.684%	$48.4575	$48.46	$48.45	$48.50
7 purchase totals =	$748.43		$803.8797	$803.89	$803.90	$803.90