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	$129.95	10.708%	$143.865	$143.87	$143.85	$143.90
Purchase #2	$43.83	4.438%	$45.7752	$45.78	$45.80	$45.80
Purchase #3	$54.74	10.604%	$60.5446	$60.54	$60.55	$60.50
Purchase #4	$53.57	3.641%	$55.5205	$55.52	$55.50	$55.50
Purchase #5	$142.71	6.215%	$151.5794	$151.58	$151.60	$151.60
Purchase #6	$113.65	3.762%	$117.9255	$117.93	$117.95	$117.90
Purchase #7	$111.31	13.176%	$125.9762	$125.98	$126.00	$126.00
7 purchase totals =	$649.76		$701.1864	$701.20	$701.25	$701.20