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	$6.97	6.691%	$7.4364	$7.44	$7.45	$7.40
Purchase #2	$59.77	10.566%	$66.0853	$66.09	$66.10	$66.10
Purchase #3	$94.45	5.341%	$99.4946	$99.49	$99.50	$99.50
Purchase #4	$200.57	6.505%	$213.6171	$213.62	$213.60	$213.60
Purchase #5	$91.94	7.477%	$98.8144	$98.81	$98.80	$98.80
Purchase #6	$183.83	4.624%	$192.3303	$192.33	$192.35	$192.30
Purchase #7	$229.95	11.299%	$255.9321	$255.93	$255.95	$255.90
7 purchase totals =	$867.48		$933.7102	$933.71	$933.75	$933.60