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	$56.43	13.185%	$63.8703	$63.87	$63.85	$63.90
Purchase #2	$165.58	9.162%	$180.7504	$180.75	$180.75	$180.80
Purchase #3	$20.97	4.531%	$21.9202	$21.92	$21.90	$21.90
Purchase #4	$96.30	7.462%	$103.4859	$103.49	$103.50	$103.50
Purchase #5	$173.88	6.733%	$185.5873	$185.59	$185.60	$185.60
Purchase #6	$95.88	4.812%	$100.4937	$100.49	$100.50	$100.50
Purchase #7	$241.70	11.528%	$269.5632	$269.56	$269.55	$269.60
7 purchase totals =	$850.74		$925.6710	$925.67	$925.65	$925.80