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	$71.58	3.491%	$74.0789	$74.08	$74.10	$74.10
Purchase #2	$122.60	7.237%	$131.4726	$131.47	$131.45	$131.50
Purchase #3	$225.51	12.391%	$253.4529	$253.45	$253.45	$253.50
Purchase #4	$91.64	10.153%	$100.9442	$100.94	$100.95	$100.90
Purchase #5	$112.28	9.620%	$123.0813	$123.08	$123.10	$123.10
Purchase #6	$29.92	11.546%	$33.3746	$33.37	$33.35	$33.40
Purchase #7	$44.70	8.142%	$48.3395	$48.34	$48.35	$48.30
7 purchase totals =	$698.23		$764.7440	$764.73	$764.75	$764.80