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	$57.75	13.338%	$65.4527	$65.45	$65.45	$65.50
Purchase #2	$239.46	7.249%	$256.8185	$256.82	$256.80	$256.80
Purchase #3	$85.92	5.197%	$90.3853	$90.39	$90.40	$90.40
Purchase #4	$86.29	10.273%	$95.1546	$95.15	$95.15	$95.20
Purchase #5	$242.70	12.318%	$272.5958	$272.60	$272.60	$272.60
Purchase #6	$111.61	10.646%	$123.492	$123.49	$123.50	$123.50
Purchase #7	$143.34	7.716%	$154.4001	$154.40	$154.40	$154.40
7 purchase totals =	$967.07		$1,058.2990	$1,058.30	$1,058.30	$1,058.40