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	$141.92	4.477%	$148.2738	$148.27	$148.25	$148.30
Purchase #2	$238.59	13.178%	$270.0314	$270.03	$270.05	$270.00
Purchase #3	$139.78	8.438%	$151.5746	$151.57	$151.55	$151.60
Purchase #4	$15.95	10.759%	$17.6661	$17.67	$17.65	$17.70
Purchase #5	$171.83	6.442%	$182.8993	$182.90	$182.90	$182.90
Purchase #6	$40.98	6.420%	$43.6109	$43.61	$43.60	$43.60
Purchase #7	$45.27	3.296%	$46.7621	$46.76	$46.75	$46.80
7 purchase totals =	$794.32		$860.8182	$860.81	$860.75	$860.90