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	$192.39	6.583%	$205.055	$205.06	$205.05	$205.10
Purchase #2	$194.30	8.593%	$210.9962	$211.00	$211.00	$211.00
Purchase #3	$171.93	4.280%	$179.2886	$179.29	$179.30	$179.30
Purchase #4	$138.32	12.434%	$155.5187	$155.52	$155.50	$155.50
Purchase #5	$73.83	6.480%	$78.6142	$78.61	$78.60	$78.60
Purchase #6	$88.88	7.103%	$95.1931	$95.19	$95.20	$95.20
Purchase #7	$29.45	7.846%	$31.7606	$31.76	$31.75	$31.80
7 purchase totals =	$889.10		$956.4264	$956.43	$956.40	$956.50