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	$238.67	8.772%	$259.6061	$259.61	$259.60	$259.60
Purchase #2	$176.95	7.767%	$190.6937	$190.69	$190.70	$190.70
Purchase #3	$70.61	11.725%	$78.889	$78.89	$78.90	$78.90
Purchase #4	$49.84	12.690%	$56.1647	$56.16	$56.15	$56.20
Purchase #5	$204.43	13.157%	$231.3269	$231.33	$231.35	$231.30
Purchase #6	$57.27	13.310%	$64.8926	$64.89	$64.90	$64.90
Purchase #7	$190.38	4.583%	$199.1051	$199.11	$199.10	$199.10
7 purchase totals =	$988.15		$1,080.6781	$1,080.68	$1,080.70	$1,080.70