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	$131.94	13.818%	$150.1715	$150.17	$150.15	$150.20
Purchase #2	$137.83	13.164%	$155.9739	$155.97	$155.95	$156.00
Purchase #3	$67.59	5.705%	$71.446	$71.45	$71.45	$71.40
Purchase #4	$62.71	7.413%	$67.3587	$67.36	$67.35	$67.40
Purchase #5	$70.81	9.602%	$77.6092	$77.61	$77.60	$77.60
Purchase #6	$241.87	8.164%	$261.6163	$261.62	$261.60	$261.60
Purchase #7	$104.59	6.852%	$111.7565	$111.76	$111.75	$111.80
7 purchase totals =	$817.34		$895.9321	$895.94	$895.85	$896.00