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	$98.52	10.380%	$108.7464	$108.75	$108.75	$108.70
Purchase #2	$15.33	10.186%	$16.8915	$16.89	$16.90	$16.90
Purchase #3	$10.89	4.551%	$11.3856	$11.39	$11.40	$11.40
Purchase #4	$153.47	3.406%	$158.6972	$158.70	$158.70	$158.70
Purchase #5	$171.60	3.680%	$177.9149	$177.91	$177.90	$177.90
Purchase #6	$238.27	7.383%	$255.8615	$255.86	$255.85	$255.90
Purchase #7	$57.70	3.168%	$59.5279	$59.53	$59.55	$59.50
7 purchase totals =	$745.78		$789.0250	$789.03	$789.05	$789.00