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	$152.38	9.734%	$167.2127	$167.21	$167.20	$167.20
Purchase #2	$126.83	10.255%	$139.8364	$139.84	$139.85	$139.80
Purchase #3	$82.59	9.254%	$90.2329	$90.23	$90.25	$90.20
Purchase #4	$19.59	11.301%	$21.8039	$21.80	$21.80	$21.80
Purchase #5	$133.94	8.103%	$144.7932	$144.79	$144.80	$144.80
Purchase #6	$145.75	5.450%	$153.6934	$153.69	$153.70	$153.70
Purchase #7	$134.78	12.699%	$151.8957	$151.90	$151.90	$151.90
7 purchase totals =	$795.86		$869.4682	$869.46	$869.50	$869.40