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	$166.89	3.551%	$172.8163	$172.82	$172.80	$172.80
Purchase #2	$90.94	4.478%	$95.0123	$95.01	$95.00	$95.00
Purchase #3	$231.59	11.218%	$257.5698	$257.57	$257.55	$257.60
Purchase #4	$172.97	9.172%	$188.8348	$188.83	$188.85	$188.80
Purchase #5	$120.76	13.493%	$137.0541	$137.05	$137.05	$137.10
Purchase #6	$202.76	11.168%	$225.4042	$225.40	$225.40	$225.40
Purchase #7	$154.43	13.703%	$175.5915	$175.59	$175.60	$175.60
7 purchase totals =	$1,140.34		$1,252.2830	$1,252.27	$1,252.25	$1,252.30