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	$95.86	5.646%	$101.2723	$101.27	$101.25	$101.30
Purchase #2	$104.60	11.649%	$116.7849	$116.78	$116.80	$116.80
Purchase #3	$138.52	3.820%	$143.8115	$143.81	$143.80	$143.80
Purchase #4	$195.64	13.737%	$222.5151	$222.52	$222.50	$222.50
Purchase #5	$173.36	8.469%	$188.0419	$188.04	$188.05	$188.00
Purchase #6	$229.69	11.617%	$256.3731	$256.37	$256.35	$256.40
Purchase #7	$133.40	7.648%	$143.6024	$143.60	$143.60	$143.60
7 purchase totals =	$1,071.07		$1,172.4012	$1,172.39	$1,172.35	$1,172.40