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	$139.95	10.514%	$154.6643	$154.66	$154.65	$154.70
Purchase #2	$189.58	12.207%	$212.722	$212.72	$212.70	$212.70
Purchase #3	$211.39	3.433%	$218.647	$218.65	$218.65	$218.60
Purchase #4	$187.56	4.698%	$196.3716	$196.37	$196.35	$196.40
Purchase #5	$127.94	9.733%	$140.3924	$140.39	$140.40	$140.40
Purchase #6	$11.76	13.697%	$13.3708	$13.37	$13.35	$13.40
Purchase #7	$111.77	13.844%	$127.2434	$127.24	$127.25	$127.20
7 purchase totals =	$979.95		$1,063.4115	$1,063.40	$1,063.35	$1,063.40