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	$52.30	10.342%	$57.7089	$57.71	$57.70	$57.70
Purchase #2	$228.82	6.865%	$244.5285	$244.53	$244.55	$244.50
Purchase #3	$130.77	9.387%	$143.0454	$143.05	$143.05	$143.00
Purchase #4	$154.92	3.577%	$160.4615	$160.46	$160.45	$160.50
Purchase #5	$183.88	13.588%	$208.8656	$208.87	$208.85	$208.90
Purchase #6	$34.75	10.656%	$38.453	$38.45	$38.45	$38.50
Purchase #7	$89.50	5.528%	$94.4476	$94.45	$94.45	$94.40
7 purchase totals =	$874.94		$947.5105	$947.52	$947.50	$947.50