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	$183.33	13.537%	$208.1474	$208.15	$208.15	$208.10
Purchase #2	$137.59	11.572%	$153.5119	$153.51	$153.50	$153.50
Purchase #3	$158.60	3.403%	$163.9972	$164.00	$164.00	$164.00
Purchase #4	$112.77	3.826%	$117.0846	$117.08	$117.10	$117.10
Purchase #5	$120.50	13.344%	$136.5795	$136.58	$136.60	$136.60
Purchase #6	$18.97	11.466%	$21.1451	$21.15	$21.15	$21.10
Purchase #7	$98.57	5.462%	$103.9539	$103.95	$103.95	$104.00
7 purchase totals =	$830.33		$904.4196	$904.42	$904.45	$904.40