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	$249.97	9.147%	$272.8348	$272.83	$272.85	$272.80
Purchase #2	$196.55	11.461%	$219.0766	$219.08	$219.10	$219.10
Purchase #3	$178.55	8.824%	$194.3053	$194.31	$194.30	$194.30
Purchase #4	$106.88	5.262%	$112.504	$112.50	$112.50	$112.50
Purchase #5	$94.51	12.655%	$106.4702	$106.47	$106.45	$106.50
Purchase #6	$132.42	7.592%	$142.4733	$142.47	$142.45	$142.50
Purchase #7	$63.69	4.393%	$66.4879	$66.49	$66.50	$66.50
7 purchase totals =	$1,022.57		$1,114.1521	$1,114.15	$1,114.15	$1,114.20