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	$200.68	10.647%	$222.0464	$222.05	$222.05	$222.00
Purchase #2	$236.51	5.481%	$249.4731	$249.47	$249.45	$249.50
Purchase #3	$187.48	11.716%	$209.4452	$209.45	$209.45	$209.40
Purchase #4	$109.34	7.763%	$117.8281	$117.83	$117.85	$117.80
Purchase #5	$139.95	7.262%	$150.1132	$150.11	$150.10	$150.10
Purchase #6	$17.70	9.496%	$19.3808	$19.38	$19.40	$19.40
Purchase #7	$37.65	6.737%	$40.1865	$40.19	$40.20	$40.20
7 purchase totals =	$929.31		$1,008.4733	$1,008.48	$1,008.50	$1,008.40