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	$30.99	8.627%	$33.6635	$33.66	$33.65	$33.70
Purchase #2	$112.28	4.683%	$117.5381	$117.54	$117.55	$117.50
Purchase #3	$51.29	6.407%	$54.5762	$54.58	$54.60	$54.60
Purchase #4	$94.74	9.811%	$104.0349	$104.03	$104.05	$104.00
Purchase #5	$87.59	12.291%	$98.3557	$98.36	$98.35	$98.40
Purchase #6	$148.33	13.861%	$168.89	$168.89	$168.90	$168.90
Purchase #7	$113.59	4.590%	$118.8038	$118.80	$118.80	$118.80
7 purchase totals =	$638.81		$695.8622	$695.86	$695.90	$695.90