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	$139.52	13.838%	$158.8268	$158.83	$158.85	$158.80
Purchase #2	$39.46	7.113%	$42.2668	$42.27	$42.25	$42.30
Purchase #3	$47.55	8.637%	$51.6569	$51.66	$51.65	$51.70
Purchase #4	$150.99	7.622%	$162.4985	$162.50	$162.50	$162.50
Purchase #5	$235.52	4.246%	$245.5202	$245.52	$245.50	$245.50
Purchase #6	$167.61	13.593%	$190.3932	$190.39	$190.40	$190.40
Purchase #7	$50.59	12.768%	$57.0493	$57.05	$57.05	$57.00
7 purchase totals =	$831.24		$908.2117	$908.22	$908.20	$908.20