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	$69.70	4.536%	$72.8616	$72.86	$72.85	$72.90
Purchase #2	$177.86	9.649%	$195.0217	$195.02	$195.00	$195.00
Purchase #3	$108.66	12.167%	$121.8807	$121.88	$121.90	$121.90
Purchase #4	$20.89	12.493%	$23.4998	$23.50	$23.50	$23.50
Purchase #5	$95.40	3.781%	$99.0071	$99.01	$99.00	$99.00
Purchase #6	$153.25	9.611%	$167.9789	$167.98	$168.00	$168.00
Purchase #7	$25.47	12.318%	$28.6074	$28.61	$28.60	$28.60
7 purchase totals =	$651.23		$708.8572	$708.86	$708.85	$708.90