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	$153.39	9.584%	$168.0909	$168.09	$168.10	$168.10
Purchase #2	$225.97	3.730%	$234.3987	$234.40	$234.40	$234.40
Purchase #3	$108.58	7.622%	$116.856	$116.86	$116.85	$116.90
Purchase #4	$29.92	13.725%	$34.0265	$34.03	$34.05	$34.00
Purchase #5	$83.86	6.643%	$89.4308	$89.43	$89.45	$89.40
Purchase #6	$236.65	12.575%	$266.4087	$266.41	$266.40	$266.40
Purchase #7	$143.86	8.683%	$156.3514	$156.35	$156.35	$156.40
7 purchase totals =	$982.23		$1,065.5630	$1,065.57	$1,065.60	$1,065.60