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	$177.49	4.143%	$184.8434	$184.84	$184.85	$184.80
Purchase #2	$73.37	7.205%	$78.6563	$78.66	$78.65	$78.70
Purchase #3	$70.83	4.232%	$73.8275	$73.83	$73.85	$73.80
Purchase #4	$148.71	6.338%	$158.1352	$158.14	$158.15	$158.10
Purchase #5	$153.40	7.729%	$165.2563	$165.26	$165.25	$165.30
Purchase #6	$57.52	9.733%	$63.1184	$63.12	$63.10	$63.10
Purchase #7	$33.37	12.821%	$37.6484	$37.65	$37.65	$37.60
7 purchase totals =	$714.69		$761.4855	$761.50	$761.50	$761.40