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	$10.81	3.154%	$11.1509	$11.15	$11.15	$11.20
Purchase #2	$50.60	3.270%	$52.2546	$52.25	$52.25	$52.30
Purchase #3	$192.25	12.263%	$215.8256	$215.83	$215.85	$215.80
Purchase #4	$55.71	13.351%	$63.1478	$63.15	$63.15	$63.10
Purchase #5	$17.53	8.733%	$19.0609	$19.06	$19.05	$19.10
Purchase #6	$94.28	6.373%	$100.2885	$100.29	$100.30	$100.30
Purchase #7	$196.32	12.126%	$220.1258	$220.13	$220.15	$220.10
7 purchase totals =	$617.50		$681.8541	$681.86	$681.90	$681.90