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	$162.50	11.565%	$181.2931	$181.29	$181.30	$181.30
Purchase #2	$83.97	4.191%	$87.4892	$87.49	$87.50	$87.50
Purchase #3	$198.81	13.320%	$225.2915	$225.29	$225.30	$225.30
Purchase #4	$11.78	6.186%	$12.5087	$12.51	$12.50	$12.50
Purchase #5	$30.46	13.314%	$34.5154	$34.52	$34.50	$34.50
Purchase #6	$184.59	6.521%	$196.6271	$196.63	$196.65	$196.60
Purchase #7	$42.53	12.390%	$47.7995	$47.80	$47.80	$47.80
7 purchase totals =	$714.64		$785.5245	$785.53	$785.55	$785.50