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	$62.97	7.348%	$67.597	$67.60	$67.60	$67.60
Purchase #2	$20.94	12.127%	$23.4794	$23.48	$23.50	$23.50
Purchase #3	$34.45	6.246%	$36.6017	$36.60	$36.60	$36.60
Purchase #4	$117.51	5.804%	$124.3303	$124.33	$124.35	$124.30
Purchase #5	$72.30	11.410%	$80.5494	$80.55	$80.55	$80.50
Purchase #6	$120.78	4.826%	$126.6088	$126.61	$126.60	$126.60
Purchase #7	$30.90	5.231%	$32.5164	$32.52	$32.50	$32.50
7 purchase totals =	$459.85		$491.6830	$491.69	$491.70	$491.60