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	$105.95	6.720%	$113.0698	$113.07	$113.05	$113.10
Purchase #2	$123.59	4.254%	$128.8475	$128.85	$128.85	$128.80
Purchase #3	$172.87	12.162%	$193.8944	$193.89	$193.90	$193.90
Purchase #4	$14.70	6.126%	$15.6005	$15.60	$15.60	$15.60
Purchase #5	$63.68	13.307%	$72.1539	$72.15	$72.15	$72.20
Purchase #6	$127.64	9.123%	$139.2846	$139.28	$139.30	$139.30
Purchase #7	$44.62	6.306%	$47.4337	$47.43	$47.45	$47.40
7 purchase totals =	$653.05		$710.2844	$710.27	$710.30	$710.30