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	$112.66	3.386%	$116.4747	$116.47	$116.45	$116.50
Purchase #2	$107.77	10.235%	$118.8003	$118.80	$118.80	$118.80
Purchase #3	$77.60	10.438%	$85.6999	$85.70	$85.70	$85.70
Purchase #4	$38.45	9.434%	$42.0774	$42.08	$42.10	$42.10
Purchase #5	$217.58	7.141%	$233.1174	$233.12	$233.10	$233.10
Purchase #6	$124.71	3.654%	$129.2669	$129.27	$129.25	$129.30
Purchase #7	$180.82	8.863%	$196.8461	$196.85	$196.85	$196.80
7 purchase totals =	$859.59		$922.2827	$922.29	$922.25	$922.30