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	$235.88	8.351%	$255.5783	$255.58	$255.60	$255.60
Purchase #2	$119.81	10.614%	$132.5266	$132.53	$132.55	$132.50
Purchase #3	$134.66	5.826%	$142.5053	$142.51	$142.50	$142.50
Purchase #4	$214.64	10.804%	$237.8297	$237.83	$237.85	$237.80
Purchase #5	$69.93	12.369%	$78.5796	$78.58	$78.60	$78.60
Purchase #6	$201.88	13.118%	$228.3626	$228.36	$228.35	$228.40
Purchase #7	$194.89	13.648%	$221.4886	$221.49	$221.50	$221.50
7 purchase totals =	$1,171.69		$1,296.8707	$1,296.88	$1,296.95	$1,296.90