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	$117.90	4.762%	$123.5144	$123.51	$123.50	$123.50
Purchase #2	$6.35	3.828%	$6.5931	$6.59	$6.60	$6.60
Purchase #3	$166.89	7.142%	$178.8093	$178.81	$178.80	$178.80
Purchase #4	$63.64	12.429%	$71.5498	$71.55	$71.55	$71.50
Purchase #5	$78.85	3.556%	$81.6539	$81.65	$81.65	$81.70
Purchase #6	$216.83	10.455%	$239.4996	$239.50	$239.50	$239.50
Purchase #7	$103.88	4.716%	$108.779	$108.78	$108.80	$108.80
7 purchase totals =	$754.34		$810.3991	$810.39	$810.40	$810.40