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	$40.82	12.226%	$45.8107	$45.81	$45.80	$45.80
Purchase #2	$143.29	12.175%	$160.7356	$160.74	$160.75	$160.70
Purchase #3	$196.81	5.783%	$208.1915	$208.19	$208.20	$208.20
Purchase #4	$158.45	5.850%	$167.7193	$167.72	$167.70	$167.70
Purchase #5	$207.90	4.785%	$217.848	$217.85	$217.85	$217.80
Purchase #6	$224.27	9.420%	$245.3962	$245.40	$245.40	$245.40
Purchase #7	$48.78	5.197%	$51.3151	$51.32	$51.30	$51.30
7 purchase totals =	$1,020.32		$1,097.0164	$1,097.03	$1,097.00	$1,096.90