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	$67.30	3.807%	$69.8621	$69.86	$69.85	$69.90
Purchase #2	$118.54	4.141%	$123.4487	$123.45	$123.45	$123.40
Purchase #3	$131.40	10.125%	$144.7043	$144.70	$144.70	$144.70
Purchase #4	$112.51	9.750%	$123.4797	$123.48	$123.50	$123.50
Purchase #5	$34.98	3.119%	$36.071	$36.07	$36.05	$36.10
Purchase #6	$13.94	13.517%	$15.8243	$15.82	$15.80	$15.80
Purchase #7	$99.75	4.770%	$104.5081	$104.51	$104.50	$104.50
7 purchase totals =	$578.42		$617.8982	$617.89	$617.85	$617.90