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	$140.92	7.757%	$151.8512	$151.85	$151.85	$151.90
Purchase #2	$122.31	11.768%	$136.7034	$136.70	$136.70	$136.70
Purchase #3	$112.58	3.724%	$116.7725	$116.77	$116.75	$116.80
Purchase #4	$156.78	6.716%	$167.3093	$167.31	$167.30	$167.30
Purchase #5	$103.69	9.509%	$113.5499	$113.55	$113.55	$113.50
Purchase #6	$90.28	9.411%	$98.7763	$98.78	$98.80	$98.80
Purchase #7	$95.38	5.680%	$100.7976	$100.80	$100.80	$100.80
7 purchase totals =	$821.94		$885.7602	$885.76	$885.75	$885.80