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	$89.35	11.767%	$99.8638	$99.86	$99.85	$99.90
Purchase #2	$215.64	7.340%	$231.468	$231.47	$231.45	$231.50
Purchase #3	$136.59	10.648%	$151.1341	$151.13	$151.15	$151.10
Purchase #4	$198.57	13.601%	$225.5775	$225.58	$225.60	$225.60
Purchase #5	$116.90	8.183%	$126.4659	$126.47	$126.45	$126.50
Purchase #6	$219.64	13.679%	$249.6846	$249.68	$249.70	$249.70
Purchase #7	$117.53	12.346%	$132.0403	$132.04	$132.05	$132.00
7 purchase totals =	$1,094.22		$1,216.2342	$1,216.23	$1,216.25	$1,216.30