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	$13.57	6.679%	$14.4763	$14.48	$14.50	$14.50
Purchase #2	$224.42	13.857%	$255.5179	$255.52	$255.50	$255.50
Purchase #3	$72.25	12.455%	$81.2487	$81.25	$81.25	$81.20
Purchase #4	$49.77	3.385%	$51.4547	$51.45	$51.45	$51.50
Purchase #5	$172.64	10.195%	$190.2406	$190.24	$190.25	$190.20
Purchase #6	$111.70	12.220%	$125.3497	$125.35	$125.35	$125.30
Purchase #7	$114.37	7.636%	$123.1033	$123.10	$123.10	$123.10
7 purchase totals =	$758.72		$841.3912	$841.39	$841.40	$841.30