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	$70.91	11.311%	$78.9306	$78.93	$78.95	$78.90
Purchase #2	$177.71	10.770%	$196.8494	$196.85	$196.85	$196.80
Purchase #3	$116.53	13.646%	$132.4317	$132.43	$132.45	$132.40
Purchase #4	$246.48	6.649%	$262.8685	$262.87	$262.85	$262.90
Purchase #5	$110.85	11.395%	$123.4814	$123.48	$123.50	$123.50
Purchase #6	$189.74	3.786%	$196.9236	$196.92	$196.90	$196.90
Purchase #7	$167.99	12.631%	$189.2088	$189.21	$189.20	$189.20
7 purchase totals =	$1,080.21		$1,180.6940	$1,180.69	$1,180.70	$1,180.60