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	$217.83	11.531%	$242.948	$242.95	$242.95	$242.90
Purchase #2	$173.92	8.336%	$188.418	$188.42	$188.40	$188.40
Purchase #3	$31.72	9.661%	$34.7845	$34.78	$34.80	$34.80
Purchase #4	$50.55	7.423%	$54.3023	$54.30	$54.30	$54.30
Purchase #5	$150.90	4.756%	$158.0768	$158.08	$158.10	$158.10
Purchase #6	$184.40	12.798%	$207.9995	$208.00	$208.00	$208.00
Purchase #7	$233.25	5.419%	$245.8898	$245.89	$245.90	$245.90
7 purchase totals =	$1,042.57		$1,132.4189	$1,132.42	$1,132.45	$1,132.40