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	$103.48	7.756%	$111.5059	$111.51	$111.50	$111.50
Purchase #2	$221.75	9.513%	$242.8451	$242.85	$242.85	$242.80
Purchase #3	$132.74	10.659%	$146.8888	$146.89	$146.90	$146.90
Purchase #4	$121.86	7.741%	$131.2932	$131.29	$131.30	$131.30
Purchase #5	$21.50	10.243%	$23.7022	$23.70	$23.70	$23.70
Purchase #6	$80.42	8.677%	$87.398	$87.40	$87.40	$87.40
Purchase #7	$49.42	11.207%	$54.9585	$54.96	$54.95	$55.00
7 purchase totals =	$731.17		$798.5917	$798.60	$798.60	$798.60