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	$34.96	9.448%	$38.263	$38.26	$38.25	$38.30
Purchase #2	$59.60	11.808%	$66.6376	$66.64	$66.65	$66.60
Purchase #3	$101.89	4.342%	$106.3141	$106.31	$106.30	$106.30
Purchase #4	$40.60	6.104%	$43.0782	$43.08	$43.10	$43.10
Purchase #5	$89.54	6.618%	$95.4658	$95.47	$95.45	$95.50
Purchase #6	$43.48	9.792%	$47.7376	$47.74	$47.75	$47.70
Purchase #7	$121.42	13.739%	$138.1019	$138.10	$138.10	$138.10
7 purchase totals =	$491.49		$535.5982	$535.60	$535.60	$535.60