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	$117.29	8.721%	$127.5189	$127.52	$127.50	$127.50
Purchase #2	$68.29	12.278%	$76.6746	$76.67	$76.65	$76.70
Purchase #3	$53.35	3.112%	$55.0103	$55.01	$55.00	$55.00
Purchase #4	$63.31	5.547%	$66.8218	$66.82	$66.80	$66.80
Purchase #5	$53.43	9.720%	$58.6234	$58.62	$58.60	$58.60
Purchase #6	$95.63	4.610%	$100.0385	$100.04	$100.05	$100.00
Purchase #7	$123.55	6.558%	$131.6524	$131.65	$131.65	$131.70
7 purchase totals =	$574.85		$616.3399	$616.33	$616.25	$616.30