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	$219.78	5.134%	$231.0635	$231.06	$231.05	$231.10
Purchase #2	$145.48	9.206%	$158.8729	$158.87	$158.85	$158.90
Purchase #3	$29.39	7.490%	$31.5913	$31.59	$31.60	$31.60
Purchase #4	$108.83	13.377%	$123.3882	$123.39	$123.40	$123.40
Purchase #5	$244.85	12.293%	$274.9494	$274.95	$274.95	$274.90
Purchase #6	$145.32	6.720%	$155.0855	$155.09	$155.10	$155.10
Purchase #7	$242.51	13.219%	$274.5674	$274.57	$274.55	$274.60
7 purchase totals =	$1,136.16		$1,249.5182	$1,249.52	$1,249.50	$1,249.60