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	$56.50	10.835%	$62.6218	$62.62	$62.60	$62.60
Purchase #2	$80.41	5.789%	$85.0649	$85.06	$85.05	$85.10
Purchase #3	$38.80	4.509%	$40.5495	$40.55	$40.55	$40.50
Purchase #4	$123.49	3.753%	$128.1246	$128.12	$128.10	$128.10
Purchase #5	$13.77	13.322%	$15.6044	$15.60	$15.60	$15.60
Purchase #6	$73.47	13.466%	$83.3635	$83.36	$83.35	$83.40
Purchase #7	$142.38	5.227%	$149.8222	$149.82	$149.80	$149.80
7 purchase totals =	$528.82		$565.1509	$565.13	$565.05	$565.10