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	$184.53	8.692%	$200.5693	$200.57	$200.55	$200.60
Purchase #2	$146.64	6.466%	$156.1217	$156.12	$156.10	$156.10
Purchase #3	$121.88	8.558%	$132.3105	$132.31	$132.30	$132.30
Purchase #4	$145.40	4.390%	$151.7831	$151.78	$151.80	$151.80
Purchase #5	$195.43	7.757%	$210.5895	$210.59	$210.60	$210.60
Purchase #6	$75.49	10.332%	$83.2896	$83.29	$83.30	$83.30
Purchase #7	$175.45	13.316%	$198.8129	$198.81	$198.80	$198.80
7 purchase totals =	$1,044.82		$1,133.4766	$1,133.47	$1,133.45	$1,133.50