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	$150.67	5.538%	$159.0141	$159.01	$159.00	$159.00
Purchase #2	$37.85	3.286%	$39.0938	$39.09	$39.10	$39.10
Purchase #3	$206.69	5.234%	$217.5082	$217.51	$217.50	$217.50
Purchase #4	$80.68	10.516%	$89.1643	$89.16	$89.15	$89.20
Purchase #5	$118.82	4.127%	$123.7237	$123.72	$123.70	$123.70
Purchase #6	$34.39	6.357%	$36.5762	$36.58	$36.60	$36.60
Purchase #7	$95.37	5.770%	$100.8728	$100.87	$100.85	$100.90
7 purchase totals =	$724.47		$765.9531	$765.94	$765.90	$766.00