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	$61.72	6.750%	$65.8861	$65.89	$65.90	$65.90
Purchase #2	$93.37	4.401%	$97.4792	$97.48	$97.50	$97.50
Purchase #3	$130.60	11.650%	$145.8149	$145.81	$145.80	$145.80
Purchase #4	$92.34	6.207%	$98.0715	$98.07	$98.05	$98.10
Purchase #5	$48.52	6.804%	$51.8213	$51.82	$51.80	$51.80
Purchase #6	$201.41	7.823%	$217.1663	$217.17	$217.15	$217.20
Purchase #7	$39.78	9.622%	$43.6076	$43.61	$43.60	$43.60
7 purchase totals =	$667.74		$719.8469	$719.85	$719.80	$719.90