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	$99.54	12.103%	$111.5873	$111.59	$111.60	$111.60
Purchase #2	$244.38	12.798%	$275.6558	$275.66	$275.65	$275.70
Purchase #3	$162.94	3.480%	$168.6103	$168.61	$168.60	$168.60
Purchase #4	$100.26	11.464%	$111.7538	$111.75	$111.75	$111.80
Purchase #5	$99.25	9.439%	$108.6182	$108.62	$108.60	$108.60
Purchase #6	$231.66	6.201%	$246.0252	$246.03	$246.05	$246.00
Purchase #7	$43.86	6.255%	$46.6034	$46.60	$46.60	$46.60
7 purchase totals =	$981.89		$1,068.8540	$1,068.86	$1,068.85	$1,068.90