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	$78.83	4.602%	$82.4578	$82.46	$82.45	$82.50
Purchase #2	$11.86	7.630%	$12.7649	$12.76	$12.75	$12.80
Purchase #3	$205.39	10.735%	$227.4386	$227.44	$227.45	$227.40
Purchase #4	$9.77	6.400%	$10.3953	$10.40	$10.40	$10.40
Purchase #5	$48.31	13.627%	$54.8932	$54.89	$54.90	$54.90
Purchase #6	$203.95	10.781%	$225.9378	$225.94	$225.95	$225.90
Purchase #7	$9.99	8.795%	$10.8686	$10.87	$10.85	$10.90
7 purchase totals =	$568.10		$624.7562	$624.76	$624.75	$624.80