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	$50.48	13.341%	$57.2145	$57.21	$57.20	$57.20
Purchase #2	$167.50	13.758%	$190.5447	$190.54	$190.55	$190.50
Purchase #3	$15.82	11.355%	$17.6164	$17.62	$17.60	$17.60
Purchase #4	$10.77	7.699%	$11.5992	$11.60	$11.60	$11.60
Purchase #5	$103.77	10.726%	$114.9004	$114.90	$114.90	$114.90
Purchase #6	$175.27	3.436%	$181.2923	$181.29	$181.30	$181.30
Purchase #7	$142.49	5.707%	$150.6219	$150.62	$150.60	$150.60
7 purchase totals =	$666.10		$723.7894	$723.78	$723.75	$723.70