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	$45.54	9.509%	$49.8704	$49.87	$49.85	$49.90
Purchase #2	$32.37	9.593%	$35.4753	$35.48	$35.50	$35.50
Purchase #3	$128.80	6.768%	$137.5172	$137.52	$137.50	$137.50
Purchase #4	$216.66	4.211%	$225.7836	$225.78	$225.80	$225.80
Purchase #5	$96.50	9.544%	$105.71	$105.71	$105.70	$105.70
Purchase #6	$16.55	12.207%	$18.5703	$18.57	$18.55	$18.60
Purchase #7	$144.42	6.111%	$153.2455	$153.25	$153.25	$153.20
7 purchase totals =	$680.84		$726.1723	$726.18	$726.15	$726.20