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	$115.71	9.368%	$126.5497	$126.55	$126.55	$126.50
Purchase #2	$59.79	10.808%	$66.2521	$66.25	$66.25	$66.30
Purchase #3	$92.88	11.472%	$103.5352	$103.54	$103.55	$103.50
Purchase #4	$231.33	11.238%	$257.3269	$257.33	$257.35	$257.30
Purchase #5	$133.51	3.644%	$138.3751	$138.38	$138.40	$138.40
Purchase #6	$65.96	9.190%	$72.0217	$72.02	$72.00	$72.00
Purchase #7	$138.88	4.826%	$145.5823	$145.58	$145.60	$145.60
7 purchase totals =	$838.06		$909.6430	$909.65	$909.70	$909.60