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	$87.51	4.509%	$91.4558	$91.46	$91.45	$91.50
Purchase #2	$42.78	7.776%	$46.1066	$46.11	$46.10	$46.10
Purchase #3	$105.79	9.849%	$116.2093	$116.21	$116.20	$116.20
Purchase #4	$80.92	13.175%	$91.5812	$91.58	$91.60	$91.60
Purchase #5	$51.62	5.596%	$54.5087	$54.51	$54.50	$54.50
Purchase #6	$14.30	5.782%	$15.1268	$15.13	$15.15	$15.10
Purchase #7	$10.44	10.506%	$11.5368	$11.54	$11.55	$11.50
7 purchase totals =	$393.36		$426.5252	$426.54	$426.55	$426.50