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	$236.57	11.545%	$263.882	$263.88	$263.90	$263.90
Purchase #2	$87.46	3.810%	$90.7922	$90.79	$90.80	$90.80
Purchase #3	$11.60	13.772%	$13.1976	$13.20	$13.20	$13.20
Purchase #4	$213.75	7.373%	$229.5098	$229.51	$229.50	$229.50
Purchase #5	$220.67	9.705%	$242.086	$242.09	$242.10	$242.10
Purchase #6	$77.48	8.308%	$83.917	$83.92	$83.90	$83.90
Purchase #7	$226.29	7.161%	$242.4946	$242.49	$242.50	$242.50
7 purchase totals =	$1,073.82		$1,165.8792	$1,165.88	$1,165.90	$1,165.90