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	$57.85	10.387%	$63.8589	$63.86	$63.85	$63.90
Purchase #2	$187.27	3.615%	$194.0398	$194.04	$194.05	$194.00
Purchase #3	$220.74	5.667%	$233.2493	$233.25	$233.25	$233.20
Purchase #4	$188.42	9.651%	$206.6044	$206.60	$206.60	$206.60
Purchase #5	$140.52	7.770%	$151.4384	$151.44	$151.45	$151.40
Purchase #6	$143.55	11.719%	$160.3726	$160.37	$160.35	$160.40
Purchase #7	$49.89	3.451%	$51.6117	$51.61	$51.60	$51.60
7 purchase totals =	$988.24		$1,061.1751	$1,061.17	$1,061.15	$1,061.10