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	$61.44	3.759%	$63.7495	$63.75	$63.75	$63.70
Purchase #2	$94.49	6.464%	$100.5978	$100.60	$100.60	$100.60
Purchase #3	$71.98	6.388%	$76.5781	$76.58	$76.60	$76.60
Purchase #4	$61.27	10.761%	$67.8633	$67.86	$67.85	$67.90
Purchase #5	$231.25	3.688%	$239.7785	$239.78	$239.80	$239.80
Purchase #6	$103.81	9.491%	$113.6626	$113.66	$113.65	$113.70
Purchase #7	$103.32	12.796%	$116.5408	$116.54	$116.55	$116.50
7 purchase totals =	$727.56		$778.7706	$778.77	$778.80	$778.80