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	$171.28	6.272%	$182.0227	$182.02	$182.00	$182.00
Purchase #2	$130.93	8.678%	$142.2921	$142.29	$142.30	$142.30
Purchase #3	$196.52	10.746%	$217.638	$217.64	$217.65	$217.60
Purchase #4	$62.61	9.820%	$68.7583	$68.76	$68.75	$68.80
Purchase #5	$95.89	10.389%	$105.852	$105.85	$105.85	$105.90
Purchase #6	$99.90	5.733%	$105.6273	$105.63	$105.65	$105.60
Purchase #7	$131.32	10.602%	$145.2425	$145.24	$145.25	$145.20
7 purchase totals =	$888.45		$967.4329	$967.43	$967.45	$967.40