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	$31.57	4.545%	$33.0049	$33.00	$33.00	$33.00
Purchase #2	$76.88	6.140%	$81.6004	$81.60	$81.60	$81.60
Purchase #3	$123.27	6.461%	$131.2345	$131.23	$131.25	$131.20
Purchase #4	$103.43	8.491%	$112.2122	$112.21	$112.20	$112.20
Purchase #5	$116.65	6.306%	$124.0059	$124.01	$124.00	$124.00
Purchase #6	$79.42	3.757%	$82.4038	$82.40	$82.40	$82.40
Purchase #7	$137.87	11.594%	$153.8546	$153.85	$153.85	$153.90
7 purchase totals =	$669.09		$718.3163	$718.30	$718.30	$718.30