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	$35.81	5.167%	$37.6603	$37.66	$37.65	$37.70
Purchase #2	$13.78	12.155%	$15.455	$15.46	$15.45	$15.50
Purchase #3	$110.35	8.784%	$120.0431	$120.04	$120.05	$120.00
Purchase #4	$29.29	8.619%	$31.8145	$31.81	$31.80	$31.80
Purchase #5	$238.58	7.144%	$255.6242	$255.62	$255.60	$255.60
Purchase #6	$44.31	9.756%	$48.6329	$48.63	$48.65	$48.60
Purchase #7	$103.65	10.602%	$114.639	$114.64	$114.65	$114.60
7 purchase totals =	$575.77		$623.8690	$623.86	$623.85	$623.80