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	$104.96	5.783%	$111.0298	$111.03	$111.05	$111.00
Purchase #2	$188.60	11.580%	$210.4399	$210.44	$210.45	$210.40
Purchase #3	$81.36	11.369%	$90.6098	$90.61	$90.60	$90.60
Purchase #4	$100.61	7.283%	$107.9374	$107.94	$107.95	$107.90
Purchase #5	$136.60	13.518%	$155.0656	$155.07	$155.05	$155.10
Purchase #6	$242.85	12.345%	$272.8298	$272.83	$272.85	$272.80
Purchase #7	$138.83	11.535%	$154.844	$154.84	$154.85	$154.80
7 purchase totals =	$993.81		$1,102.7563	$1,102.76	$1,102.80	$1,102.60