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	$13.45	8.138%	$14.5446	$14.54	$14.55	$14.50
Purchase #2	$96.92	6.215%	$102.9436	$102.94	$102.95	$102.90
Purchase #3	$172.47	4.262%	$179.8207	$179.82	$179.80	$179.80
Purchase #4	$134.35	8.249%	$145.4325	$145.43	$145.45	$145.40
Purchase #5	$131.49	8.610%	$142.8113	$142.81	$142.80	$142.80
Purchase #6	$240.41	4.601%	$251.4713	$251.47	$251.45	$251.50
Purchase #7	$172.44	8.733%	$187.4992	$187.50	$187.50	$187.50
7 purchase totals =	$961.53		$1,024.5232	$1,024.51	$1,024.50	$1,024.40