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	$118.38	6.830%	$126.4654	$126.47	$126.45	$126.50
Purchase #2	$63.38	4.380%	$66.156	$66.16	$66.15	$66.20
Purchase #3	$157.41	12.552%	$177.1681	$177.17	$177.15	$177.20
Purchase #4	$208.92	11.122%	$232.1561	$232.16	$232.15	$232.20
Purchase #5	$173.46	13.149%	$196.2683	$196.27	$196.25	$196.30
Purchase #6	$112.85	13.800%	$128.4233	$128.42	$128.40	$128.40
Purchase #7	$122.89	9.679%	$134.7845	$134.78	$134.80	$134.80
7 purchase totals =	$957.29		$1,061.4217	$1,061.43	$1,061.35	$1,061.60