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	$214.89	9.639%	$235.6032	$235.60	$235.60	$235.60
Purchase #2	$105.29	13.156%	$119.142	$119.14	$119.15	$119.10
Purchase #3	$98.25	13.630%	$111.6415	$111.64	$111.65	$111.60
Purchase #4	$47.81	10.484%	$52.8224	$52.82	$52.80	$52.80
Purchase #5	$99.81	6.784%	$106.5811	$106.58	$106.60	$106.60
Purchase #6	$188.72	4.690%	$197.571	$197.57	$197.55	$197.60
Purchase #7	$123.28	4.239%	$128.5058	$128.51	$128.50	$128.50
7 purchase totals =	$878.05		$951.8670	$951.86	$951.85	$951.80