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	$236.57	7.523%	$254.3672	$254.37	$254.35	$254.40
Purchase #2	$128.32	3.273%	$132.5199	$132.52	$132.50	$132.50
Purchase #3	$5.27	13.292%	$5.9705	$5.97	$5.95	$6.00
Purchase #4	$151.80	3.856%	$157.6534	$157.65	$157.65	$157.70
Purchase #5	$237.31	7.702%	$255.5876	$255.59	$255.60	$255.60
Purchase #6	$227.88	9.659%	$249.8909	$249.89	$249.90	$249.90
Purchase #7	$54.50	9.772%	$59.8257	$59.83	$59.85	$59.80
7 purchase totals =	$1,041.65		$1,115.8152	$1,115.82	$1,115.80	$1,115.90