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	$104.48	6.817%	$111.6024	$111.60	$111.60	$111.60
Purchase #2	$29.61	12.126%	$33.2005	$33.20	$33.20	$33.20
Purchase #3	$224.81	5.838%	$237.9344	$237.93	$237.95	$237.90
Purchase #4	$47.81	10.574%	$52.8654	$52.87	$52.85	$52.90
Purchase #5	$132.81	11.674%	$148.3142	$148.31	$148.30	$148.30
Purchase #6	$211.47	4.387%	$220.7472	$220.75	$220.75	$220.70
Purchase #7	$233.48	9.514%	$255.6933	$255.69	$255.70	$255.70
7 purchase totals =	$984.47		$1,060.3574	$1,060.35	$1,060.35	$1,060.30