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	$63.49	6.335%	$67.5121	$67.51	$67.50	$67.50
Purchase #2	$187.75	6.517%	$199.9857	$199.99	$200.00	$200.00
Purchase #3	$213.60	13.733%	$242.9337	$242.93	$242.95	$242.90
Purchase #4	$164.47	12.114%	$184.3939	$184.39	$184.40	$184.40
Purchase #5	$47.34	7.869%	$51.0652	$51.07	$51.05	$51.10
Purchase #6	$155.49	7.526%	$167.1922	$167.19	$167.20	$167.20
Purchase #7	$91.93	4.275%	$95.86	$95.86	$95.85	$95.90
7 purchase totals =	$924.07		$1,008.9428	$1,008.94	$1,008.95	$1,009.00