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	$49.74	12.699%	$56.0565	$56.06	$56.05	$56.10
Purchase #2	$51.60	4.543%	$53.9442	$53.94	$53.95	$53.90
Purchase #3	$87.55	13.186%	$99.0943	$99.09	$99.10	$99.10
Purchase #4	$245.27	3.509%	$253.8765	$253.88	$253.90	$253.90
Purchase #5	$152.67	3.418%	$157.8883	$157.89	$157.90	$157.90
Purchase #6	$81.76	7.684%	$88.0424	$88.04	$88.05	$88.00
Purchase #7	$170.71	9.847%	$187.5198	$187.52	$187.50	$187.50
7 purchase totals =	$839.30		$896.4220	$896.42	$896.45	$896.40