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	$102.67	9.109%	$112.0222	$112.02	$112.00	$112.00
Purchase #2	$67.83	13.348%	$76.8839	$76.88	$76.90	$76.90
Purchase #3	$104.48	4.622%	$109.3091	$109.31	$109.30	$109.30
Purchase #4	$14.45	10.314%	$15.9404	$15.94	$15.95	$15.90
Purchase #5	$214.66	5.485%	$226.4341	$226.43	$226.45	$226.40
Purchase #6	$134.34	10.189%	$148.0279	$148.03	$148.05	$148.00
Purchase #7	$205.59	9.583%	$225.2917	$225.29	$225.30	$225.30
7 purchase totals =	$844.02		$913.9093	$913.90	$913.95	$913.80