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	$128.66	11.625%	$143.6167	$143.62	$143.60	$143.60
Purchase #2	$81.56	7.636%	$87.7879	$87.79	$87.80	$87.80
Purchase #3	$198.42	7.204%	$212.7142	$212.71	$212.70	$212.70
Purchase #4	$59.40	10.827%	$65.8312	$65.83	$65.85	$65.80
Purchase #5	$197.96	3.576%	$205.039	$205.04	$205.05	$205.00
Purchase #6	$200.92	10.769%	$222.5571	$222.56	$222.55	$222.60
Purchase #7	$112.86	13.769%	$128.3997	$128.40	$128.40	$128.40
7 purchase totals =	$979.78		$1,065.9458	$1,065.95	$1,065.95	$1,065.90