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	$54.66	12.429%	$61.4537	$61.45	$61.45	$61.50
Purchase #2	$240.69	6.711%	$256.8427	$256.84	$256.85	$256.80
Purchase #3	$11.71	8.564%	$12.7128	$12.71	$12.70	$12.70
Purchase #4	$179.70	9.189%	$196.2126	$196.21	$196.20	$196.20
Purchase #5	$243.90	13.523%	$276.8826	$276.88	$276.90	$276.90
Purchase #6	$238.49	3.870%	$247.7196	$247.72	$247.70	$247.70
Purchase #7	$94.31	5.242%	$99.2537	$99.25	$99.25	$99.30
7 purchase totals =	$1,063.46		$1,151.0777	$1,151.06	$1,151.05	$1,151.10