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	$217.41	3.610%	$225.2585	$225.26	$225.25	$225.30
Purchase #2	$136.92	13.396%	$155.2618	$155.26	$155.25	$155.30
Purchase #3	$201.95	7.228%	$216.5469	$216.55	$216.55	$216.50
Purchase #4	$100.95	10.684%	$111.7355	$111.74	$111.75	$111.70
Purchase #5	$86.90	13.504%	$98.635	$98.64	$98.65	$98.60
Purchase #6	$86.27	3.379%	$89.1851	$89.19	$89.20	$89.20
Purchase #7	$121.37	8.573%	$131.7751	$131.78	$131.80	$131.80
7 purchase totals =	$951.77		$1,028.3979	$1,028.42	$1,028.45	$1,028.40