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	$205.60	7.467%	$220.9522	$220.95	$220.95	$221.00
Purchase #2	$49.82	11.378%	$55.4885	$55.49	$55.50	$55.50
Purchase #3	$100.90	8.540%	$109.5169	$109.52	$109.50	$109.50
Purchase #4	$64.50	4.856%	$67.6321	$67.63	$67.65	$67.60
Purchase #5	$116.60	8.105%	$126.0504	$126.05	$126.05	$126.10
Purchase #6	$86.51	6.188%	$91.8632	$91.86	$91.85	$91.90
Purchase #7	$60.88	11.169%	$67.6797	$67.68	$67.70	$67.70
7 purchase totals =	$684.81		$739.1830	$739.18	$739.20	$739.30