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	$116.38	9.287%	$127.1882	$127.19	$127.20	$127.20
Purchase #2	$189.44	8.210%	$204.993	$204.99	$205.00	$205.00
Purchase #3	$145.60	7.716%	$156.8345	$156.83	$156.85	$156.80
Purchase #4	$123.40	7.526%	$132.6871	$132.69	$132.70	$132.70
Purchase #5	$80.47	6.137%	$85.4084	$85.41	$85.40	$85.40
Purchase #6	$100.35	11.558%	$111.9485	$111.95	$111.95	$111.90
Purchase #7	$62.82	6.170%	$66.696	$66.70	$66.70	$66.70
7 purchase totals =	$818.46		$885.7557	$885.76	$885.80	$885.70