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	$34.76	7.777%	$37.4633	$37.46	$37.45	$37.50
Purchase #2	$113.54	7.605%	$122.1747	$122.17	$122.15	$122.20
Purchase #3	$76.64	13.676%	$87.1213	$87.12	$87.10	$87.10
Purchase #4	$131.72	4.680%	$137.8845	$137.88	$137.90	$137.90
Purchase #5	$48.54	8.733%	$52.779	$52.78	$52.80	$52.80
Purchase #6	$29.72	13.820%	$33.8273	$33.83	$33.85	$33.80
Purchase #7	$223.26	5.659%	$235.8943	$235.89	$235.90	$235.90
7 purchase totals =	$658.18		$707.1444	$707.13	$707.15	$707.20