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	$144.93	10.570%	$160.2491	$160.25	$160.25	$160.20
Purchase #2	$9.96	5.492%	$10.507	$10.51	$10.50	$10.50
Purchase #3	$200.51	11.105%	$222.7766	$222.78	$222.80	$222.80
Purchase #4	$164.80	6.749%	$175.9224	$175.92	$175.90	$175.90
Purchase #5	$94.49	11.564%	$105.4168	$105.42	$105.40	$105.40
Purchase #6	$213.93	5.845%	$226.4342	$226.43	$226.45	$226.40
Purchase #7	$29.84	5.408%	$31.4537	$31.45	$31.45	$31.50
7 purchase totals =	$858.46		$932.7598	$932.76	$932.75	$932.70