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	$165.70	4.170%	$172.6097	$172.61	$172.60	$172.60
Purchase #2	$199.71	11.721%	$223.118	$223.12	$223.10	$223.10
Purchase #3	$249.85	11.136%	$277.6733	$277.67	$277.65	$277.70
Purchase #4	$118.78	7.164%	$127.2894	$127.29	$127.30	$127.30
Purchase #5	$164.28	12.392%	$184.6376	$184.64	$184.65	$184.60
Purchase #6	$248.89	10.657%	$275.4142	$275.41	$275.40	$275.40
Purchase #7	$226.41	12.808%	$255.4086	$255.41	$255.40	$255.40
7 purchase totals =	$1,373.62		$1,516.1508	$1,516.15	$1,516.10	$1,516.10