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	$102.75	8.630%	$111.6173	$111.62	$111.60	$111.60
Purchase #2	$105.99	5.226%	$111.529	$111.53	$111.55	$111.50
Purchase #3	$246.96	13.631%	$280.6231	$280.62	$280.60	$280.60
Purchase #4	$217.52	8.286%	$235.5437	$235.54	$235.55	$235.50
Purchase #5	$35.37	9.248%	$38.641	$38.64	$38.65	$38.60
Purchase #6	$146.82	10.103%	$161.6532	$161.65	$161.65	$161.70
Purchase #7	$14.54	5.800%	$15.3833	$15.38	$15.40	$15.40
7 purchase totals =	$869.95		$954.9906	$954.98	$955.00	$954.90