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	$38.69	4.216%	$40.3212	$40.32	$40.30	$40.30
Purchase #2	$127.47	7.343%	$136.8301	$136.83	$136.85	$136.80
Purchase #3	$226.62	6.490%	$241.3276	$241.33	$241.35	$241.30
Purchase #4	$242.87	10.277%	$267.8297	$267.83	$267.85	$267.80
Purchase #5	$55.40	8.835%	$60.2946	$60.29	$60.30	$60.30
Purchase #6	$12.50	13.141%	$14.1426	$14.14	$14.15	$14.10
Purchase #7	$247.72	3.549%	$256.5116	$256.51	$256.50	$256.50
7 purchase totals =	$951.27		$1,017.2574	$1,017.25	$1,017.30	$1,017.10