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	$221.32	7.536%	$237.9987	$238.00	$238.00	$238.00
Purchase #2	$63.89	8.699%	$69.4478	$69.45	$69.45	$69.40
Purchase #3	$100.43	11.602%	$112.0819	$112.08	$112.10	$112.10
Purchase #4	$40.27	7.514%	$43.2959	$43.30	$43.30	$43.30
Purchase #5	$38.41	10.314%	$42.3716	$42.37	$42.35	$42.40
Purchase #6	$92.67	11.434%	$103.2659	$103.27	$103.25	$103.30
Purchase #7	$38.98	9.304%	$42.6067	$42.61	$42.60	$42.60
7 purchase totals =	$595.97		$651.0685	$651.08	$651.05	$651.10