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	$205.42	4.423%	$214.5057	$214.51	$214.50	$214.50
Purchase #2	$90.69	5.236%	$95.4385	$95.44	$95.45	$95.40
Purchase #3	$176.76	12.467%	$198.7967	$198.80	$198.80	$198.80
Purchase #4	$186.61	10.366%	$205.954	$205.95	$205.95	$206.00
Purchase #5	$102.34	9.426%	$111.9866	$111.99	$112.00	$112.00
Purchase #6	$103.89	7.742%	$111.9332	$111.93	$111.95	$111.90
Purchase #7	$44.50	13.474%	$50.4959	$50.50	$50.50	$50.50
7 purchase totals =	$910.21		$989.1106	$989.12	$989.15	$989.10