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	$35.38	7.487%	$38.0289	$38.03	$38.05	$38.00
Purchase #2	$242.98	13.528%	$275.8503	$275.85	$275.85	$275.90
Purchase #3	$37.61	6.785%	$40.1618	$40.16	$40.15	$40.20
Purchase #4	$40.78	12.317%	$45.8029	$45.80	$45.80	$45.80
Purchase #5	$205.58	8.334%	$222.713	$222.71	$222.70	$222.70
Purchase #6	$13.32	7.866%	$14.3678	$14.37	$14.35	$14.40
Purchase #7	$13.35	6.557%	$14.2254	$14.23	$14.25	$14.20
7 purchase totals =	$589.00		$651.1501	$651.15	$651.15	$651.20