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	$38.67	12.805%	$43.6217	$43.62	$43.60	$43.60
Purchase #2	$85.70	10.348%	$94.5682	$94.57	$94.55	$94.60
Purchase #3	$16.85	9.665%	$18.4786	$18.48	$18.50	$18.50
Purchase #4	$101.56	10.198%	$111.9171	$111.92	$111.90	$111.90
Purchase #5	$171.85	5.246%	$180.8653	$180.87	$180.85	$180.90
Purchase #6	$111.25	12.247%	$124.8748	$124.87	$124.85	$124.90
Purchase #7	$156.51	4.207%	$163.0944	$163.09	$163.10	$163.10
7 purchase totals =	$682.39		$737.4201	$737.42	$737.35	$737.50