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	$117.67	12.152%	$131.9693	$131.97	$131.95	$132.00
Purchase #2	$126.46	5.407%	$133.2977	$133.30	$133.30	$133.30
Purchase #3	$107.69	4.754%	$112.8096	$112.81	$112.80	$112.80
Purchase #4	$131.89	4.701%	$138.0901	$138.09	$138.10	$138.10
Purchase #5	$222.45	5.785%	$235.3187	$235.32	$235.30	$235.30
Purchase #6	$39.43	8.868%	$42.9267	$42.93	$42.95	$42.90
Purchase #7	$78.29	6.617%	$83.4704	$83.47	$83.45	$83.50
7 purchase totals =	$823.88		$877.8825	$877.89	$877.85	$877.90