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	$61.80	4.218%	$64.4067	$64.41	$64.40	$64.40
Purchase #2	$49.58	9.291%	$54.1865	$54.19	$54.20	$54.20
Purchase #3	$104.65	6.660%	$111.6197	$111.62	$111.60	$111.60
Purchase #4	$47.39	5.248%	$49.877	$49.88	$49.90	$49.90
Purchase #5	$130.78	3.119%	$134.859	$134.86	$134.85	$134.90
Purchase #6	$58.86	6.762%	$62.8401	$62.84	$62.85	$62.80
Purchase #7	$245.65	8.549%	$266.6506	$266.65	$266.65	$266.70
7 purchase totals =	$698.71		$744.4396	$744.45	$744.45	$744.50