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	$52.56	7.307%	$56.4006	$56.40	$56.40	$56.40
Purchase #2	$225.47	10.602%	$249.3743	$249.37	$249.35	$249.40
Purchase #3	$105.39	3.327%	$108.8963	$108.90	$108.90	$108.90
Purchase #4	$207.57	5.316%	$218.6044	$218.60	$218.60	$218.60
Purchase #5	$191.26	12.837%	$215.812	$215.81	$215.80	$215.80
Purchase #6	$13.77	5.329%	$14.5038	$14.50	$14.50	$14.50
Purchase #7	$200.92	11.392%	$223.8088	$223.81	$223.80	$223.80
7 purchase totals =	$996.94		$1,087.4002	$1,087.39	$1,087.35	$1,087.40