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	$165.63	4.208%	$172.5997	$172.60	$172.60	$172.60
Purchase #2	$112.38	8.151%	$121.5401	$121.54	$121.55	$121.50
Purchase #3	$47.47	9.693%	$52.0713	$52.07	$52.05	$52.10
Purchase #4	$81.99	10.817%	$90.8589	$90.86	$90.85	$90.90
Purchase #5	$249.58	13.567%	$283.4405	$283.44	$283.45	$283.40
Purchase #6	$231.35	10.647%	$255.9818	$255.98	$256.00	$256.00
Purchase #7	$19.92	7.836%	$21.4809	$21.48	$21.50	$21.50
7 purchase totals =	$908.32		$997.9732	$997.97	$998.00	$998.00