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	$40.32	8.366%	$43.6932	$43.69	$43.70	$43.70
Purchase #2	$124.44	5.648%	$131.4684	$131.47	$131.45	$131.50
Purchase #3	$192.93	7.284%	$206.983	$206.98	$207.00	$207.00
Purchase #4	$76.31	9.189%	$83.3221	$83.32	$83.30	$83.30
Purchase #5	$193.90	6.143%	$205.8113	$205.81	$205.80	$205.80
Purchase #6	$241.66	8.596%	$262.4331	$262.43	$262.45	$262.40
Purchase #7	$136.26	5.167%	$143.3006	$143.30	$143.30	$143.30
7 purchase totals =	$1,005.82		$1,077.0117	$1,077.00	$1,077.00	$1,077.00