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	$62.54	13.671%	$71.0898	$71.09	$71.10	$71.10
Purchase #2	$83.50	8.646%	$90.7194	$90.72	$90.70	$90.70
Purchase #3	$228.69	7.688%	$246.2717	$246.27	$246.25	$246.30
Purchase #4	$234.59	10.244%	$258.6214	$258.62	$258.60	$258.60
Purchase #5	$163.69	10.489%	$180.8594	$180.86	$180.85	$180.90
Purchase #6	$238.86	13.247%	$270.5018	$270.50	$270.50	$270.50
Purchase #7	$235.66	3.677%	$244.3252	$244.33	$244.35	$244.30
7 purchase totals =	$1,247.53		$1,362.3887	$1,362.39	$1,362.35	$1,362.40