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	$52.87	12.874%	$59.6765	$59.68	$59.70	$59.70
Purchase #2	$38.45	4.321%	$40.1114	$40.11	$40.10	$40.10
Purchase #3	$38.56	9.466%	$42.2101	$42.21	$42.20	$42.20
Purchase #4	$127.52	11.438%	$142.1057	$142.11	$142.10	$142.10
Purchase #5	$185.43	4.294%	$193.3924	$193.39	$193.40	$193.40
Purchase #6	$149.70	10.669%	$165.6715	$165.67	$165.65	$165.70
Purchase #7	$9.55	9.399%	$10.4476	$10.45	$10.45	$10.40
7 purchase totals =	$602.08		$653.6152	$653.62	$653.60	$653.60