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	$119.47	5.776%	$126.3706	$126.37	$126.35	$126.40
Purchase #2	$31.60	5.580%	$33.3633	$33.36	$33.35	$33.40
Purchase #3	$211.80	7.469%	$227.6193	$227.62	$227.60	$227.60
Purchase #4	$92.59	13.631%	$105.2109	$105.21	$105.20	$105.20
Purchase #5	$194.98	11.718%	$217.8278	$217.83	$217.85	$217.80
Purchase #6	$16.67	10.523%	$18.4242	$18.42	$18.40	$18.40
Purchase #7	$97.67	7.642%	$105.1339	$105.13	$105.15	$105.10
7 purchase totals =	$764.78		$833.9500	$833.94	$833.90	$833.90