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	$58.39	5.387%	$61.5355	$61.54	$61.55	$61.50
Purchase #2	$36.48	12.364%	$40.9904	$40.99	$41.00	$41.00
Purchase #3	$154.65	11.777%	$172.8631	$172.86	$172.85	$172.90
Purchase #4	$116.62	5.868%	$123.4633	$123.46	$123.45	$123.50
Purchase #5	$205.37	9.854%	$225.6072	$225.61	$225.60	$225.60
Purchase #6	$48.57	6.128%	$51.5464	$51.55	$51.55	$51.50
Purchase #7	$59.83	13.246%	$67.7551	$67.76	$67.75	$67.80
7 purchase totals =	$679.91		$743.7610	$743.77	$743.75	$743.80