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	$208.92	8.833%	$227.3739	$227.37	$227.35	$227.40
Purchase #2	$70.28	5.414%	$74.085	$74.09	$74.10	$74.10
Purchase #3	$77.56	4.261%	$80.8648	$80.86	$80.85	$80.90
Purchase #4	$80.35	11.693%	$89.7453	$89.75	$89.75	$89.70
Purchase #5	$169.90	12.327%	$190.8436	$190.84	$190.85	$190.80
Purchase #6	$97.26	4.308%	$101.45	$101.45	$101.45	$101.50
Purchase #7	$92.77	8.291%	$100.4616	$100.46	$100.45	$100.50
7 purchase totals =	$797.04		$864.8242	$864.82	$864.80	$864.90