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	$246.47	5.620%	$260.3216	$260.32	$260.30	$260.30
Purchase #2	$151.89	8.458%	$164.7369	$164.74	$164.75	$164.70
Purchase #3	$171.38	8.638%	$186.1838	$186.18	$186.20	$186.20
Purchase #4	$40.59	5.660%	$42.8874	$42.89	$42.90	$42.90
Purchase #5	$48.60	6.868%	$51.9378	$51.94	$51.95	$51.90
Purchase #6	$103.98	13.102%	$117.6035	$117.60	$117.60	$117.60
Purchase #7	$246.95	6.256%	$262.3992	$262.40	$262.40	$262.40
7 purchase totals =	$1,009.86		$1,086.0702	$1,086.07	$1,086.10	$1,086.00