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	$223.34	3.607%	$231.3959	$231.40	$231.40	$231.40
Purchase #2	$161.81	8.753%	$175.9732	$175.97	$175.95	$176.00
Purchase #3	$105.60	5.799%	$111.7237	$111.72	$111.70	$111.70
Purchase #4	$20.78	4.405%	$21.6954	$21.70	$21.70	$21.70
Purchase #5	$202.62	10.291%	$223.4716	$223.47	$223.45	$223.50
Purchase #6	$206.32	3.176%	$212.8727	$212.87	$212.85	$212.90
Purchase #7	$66.34	9.339%	$72.5355	$72.54	$72.55	$72.50
7 purchase totals =	$986.81		$1,049.6680	$1,049.67	$1,049.60	$1,049.70