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	$134.78	13.477%	$152.9443	$152.94	$152.95	$152.90
Purchase #2	$111.79	8.619%	$121.4252	$121.43	$121.45	$121.40
Purchase #3	$201.73	10.574%	$223.0609	$223.06	$223.05	$223.10
Purchase #4	$62.76	7.513%	$67.4752	$67.48	$67.50	$67.50
Purchase #5	$220.86	11.389%	$246.0137	$246.01	$246.00	$246.00
Purchase #6	$237.73	7.301%	$255.0867	$255.09	$255.10	$255.10
Purchase #7	$63.57	5.292%	$66.9341	$66.93	$66.95	$66.90
7 purchase totals =	$1,033.22		$1,132.9401	$1,132.94	$1,133.00	$1,132.90