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	$109.94	8.822%	$119.6389	$119.64	$119.65	$119.60
Purchase #2	$216.81	5.188%	$228.0581	$228.06	$228.05	$228.10
Purchase #3	$131.99	10.730%	$146.1525	$146.15	$146.15	$146.20
Purchase #4	$105.62	13.231%	$119.5946	$119.59	$119.60	$119.60
Purchase #5	$126.62	3.345%	$130.8554	$130.86	$130.85	$130.90
Purchase #6	$43.77	8.630%	$47.5474	$47.55	$47.55	$47.50
Purchase #7	$121.98	4.459%	$127.4191	$127.42	$127.40	$127.40
7 purchase totals =	$856.73		$919.2660	$919.27	$919.25	$919.30