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	$13.27	9.564%	$14.5391	$14.54	$14.55	$14.50
Purchase #2	$127.63	7.770%	$137.5469	$137.55	$137.55	$137.50
Purchase #3	$30.30	13.381%	$34.3544	$34.35	$34.35	$34.40
Purchase #4	$25.80	12.492%	$29.0229	$29.02	$29.00	$29.00
Purchase #5	$37.83	12.724%	$42.6435	$42.64	$42.65	$42.60
Purchase #6	$95.74	4.653%	$100.1948	$100.19	$100.20	$100.20
Purchase #7	$81.71	12.105%	$91.601	$91.60	$91.60	$91.60
7 purchase totals =	$412.28		$449.9026	$449.89	$449.90	$449.80