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	$99.47	12.214%	$111.6193	$111.62	$111.60	$111.60
Purchase #2	$227.72	4.586%	$238.1632	$238.16	$238.15	$238.20
Purchase #3	$9.72	4.436%	$10.1512	$10.15	$10.15	$10.20
Purchase #4	$199.44	9.411%	$218.2093	$218.21	$218.20	$218.20
Purchase #5	$108.69	7.357%	$116.6863	$116.69	$116.70	$116.70
Purchase #6	$95.49	9.170%	$104.2464	$104.25	$104.25	$104.20
Purchase #7	$194.28	11.828%	$217.2594	$217.26	$217.25	$217.30
7 purchase totals =	$934.81		$1,016.3351	$1,016.34	$1,016.30	$1,016.40