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	$118.78	7.462%	$127.6434	$127.64	$127.65	$127.60
Purchase #2	$63.32	4.647%	$66.2625	$66.26	$66.25	$66.30
Purchase #3	$96.93	5.459%	$102.2214	$102.22	$102.20	$102.20
Purchase #4	$164.81	6.482%	$175.493	$175.49	$175.50	$175.50
Purchase #5	$35.66	9.763%	$39.1415	$39.14	$39.15	$39.10
Purchase #6	$101.51	12.770%	$114.4728	$114.47	$114.45	$114.50
Purchase #7	$129.42	9.235%	$141.3719	$141.37	$141.35	$141.40
7 purchase totals =	$710.43		$766.6065	$766.59	$766.55	$766.60