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	$208.52	4.492%	$217.8867	$217.89	$217.90	$217.90
Purchase #2	$107.28	11.378%	$119.4863	$119.49	$119.50	$119.50
Purchase #3	$6.78	5.404%	$7.1464	$7.15	$7.15	$7.10
Purchase #4	$13.83	6.756%	$14.7644	$14.76	$14.75	$14.80
Purchase #5	$34.80	5.185%	$36.6044	$36.60	$36.60	$36.60
Purchase #6	$81.79	13.269%	$92.6427	$92.64	$92.65	$92.60
Purchase #7	$168.32	13.176%	$190.4978	$190.50	$190.50	$190.50
7 purchase totals =	$621.32		$679.0287	$679.03	$679.05	$679.00