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	$199.41	11.663%	$222.6672	$222.67	$222.65	$222.70
Purchase #2	$68.68	5.189%	$72.2438	$72.24	$72.25	$72.20
Purchase #3	$14.45	9.811%	$15.8677	$15.87	$15.85	$15.90
Purchase #4	$69.96	10.806%	$77.5199	$77.52	$77.50	$77.50
Purchase #5	$172.88	8.505%	$187.5834	$187.58	$187.60	$187.60
Purchase #6	$133.52	12.640%	$150.3969	$150.40	$150.40	$150.40
Purchase #7	$158.41	12.225%	$177.7756	$177.78	$177.80	$177.80
7 purchase totals =	$817.31		$904.0545	$904.06	$904.05	$904.10