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	$77.66	10.232%	$85.6062	$85.61	$85.60	$85.60
Purchase #2	$91.61	3.615%	$94.9217	$94.92	$94.90	$94.90
Purchase #3	$174.27	11.784%	$194.806	$194.81	$194.80	$194.80
Purchase #4	$104.95	10.711%	$116.1912	$116.19	$116.20	$116.20
Purchase #5	$165.32	5.156%	$173.8439	$173.84	$173.85	$173.80
Purchase #6	$126.77	13.206%	$143.5112	$143.51	$143.50	$143.50
Purchase #7	$50.94	3.155%	$52.5472	$52.55	$52.55	$52.50
7 purchase totals =	$791.52		$861.4274	$861.43	$861.40	$861.30