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	$51.92	4.611%	$54.314	$54.31	$54.30	$54.30
Purchase #2	$11.86	3.158%	$12.2345	$12.23	$12.25	$12.20
Purchase #3	$46.61	5.468%	$49.1586	$49.16	$49.15	$49.20
Purchase #4	$72.29	10.779%	$80.0821	$80.08	$80.10	$80.10
Purchase #5	$40.87	5.208%	$42.9985	$43.00	$43.00	$43.00
Purchase #6	$124.62	5.390%	$131.337	$131.34	$131.35	$131.30
Purchase #7	$178.35	10.159%	$196.4686	$196.47	$196.45	$196.50
7 purchase totals =	$526.52		$566.5933	$566.59	$566.60	$566.60