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	$14.72	5.319%	$15.503	$15.50	$15.50	$15.50
Purchase #2	$105.48	11.533%	$117.645	$117.65	$117.65	$117.60
Purchase #3	$169.30	13.756%	$192.5889	$192.59	$192.60	$192.60
Purchase #4	$176.94	10.854%	$196.1451	$196.15	$196.15	$196.10
Purchase #5	$212.67	10.277%	$234.5261	$234.53	$234.55	$234.50
Purchase #6	$149.51	11.186%	$166.2342	$166.23	$166.25	$166.20
Purchase #7	$233.32	9.292%	$255.0001	$255.00	$255.00	$255.00
7 purchase totals =	$1,061.94		$1,177.6424	$1,177.65	$1,177.70	$1,177.50