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	$22.45	13.443%	$25.468	$25.47	$25.45	$25.50
Purchase #2	$133.85	12.381%	$150.422	$150.42	$150.40	$150.40
Purchase #3	$212.27	6.310%	$225.6642	$225.66	$225.65	$225.70
Purchase #4	$33.72	9.228%	$36.8317	$36.83	$36.85	$36.80
Purchase #5	$23.64	7.702%	$25.4608	$25.46	$25.45	$25.50
Purchase #6	$166.63	5.143%	$175.1998	$175.20	$175.20	$175.20
Purchase #7	$25.70	11.509%	$28.6578	$28.66	$28.65	$28.70
7 purchase totals =	$618.26		$667.7043	$667.70	$667.65	$667.80