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	$199.77	11.556%	$222.8554	$222.86	$222.85	$222.90
Purchase #2	$41.80	6.756%	$44.624	$44.62	$44.60	$44.60
Purchase #3	$241.36	12.337%	$271.1366	$271.14	$271.15	$271.10
Purchase #4	$93.86	4.490%	$98.0743	$98.07	$98.05	$98.10
Purchase #5	$113.93	8.186%	$123.2563	$123.26	$123.25	$123.30
Purchase #6	$103.88	12.105%	$116.4547	$116.45	$116.45	$116.50
Purchase #7	$111.79	5.478%	$117.9139	$117.91	$117.90	$117.90
7 purchase totals =	$906.39		$994.3152	$994.31	$994.25	$994.40