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	$158.57	5.472%	$167.247	$167.25	$167.25	$167.20
Purchase #2	$153.27	8.634%	$166.5033	$166.50	$166.50	$166.50
Purchase #3	$151.38	3.598%	$156.8267	$156.83	$156.85	$156.80
Purchase #4	$211.85	4.595%	$221.5845	$221.58	$221.60	$221.60
Purchase #5	$122.63	8.534%	$133.0952	$133.10	$133.10	$133.10
Purchase #6	$40.56	6.178%	$43.0658	$43.07	$43.05	$43.10
Purchase #7	$200.97	10.709%	$222.4919	$222.49	$222.50	$222.50
7 purchase totals =	$1,039.23		$1,110.8144	$1,110.82	$1,110.85	$1,110.80