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	$46.50	3.611%	$48.1791	$48.18	$48.20	$48.20
Purchase #2	$34.38	10.798%	$38.0924	$38.09	$38.10	$38.10
Purchase #3	$181.93	5.244%	$191.4704	$191.47	$191.45	$191.50
Purchase #4	$72.55	11.709%	$81.0449	$81.04	$81.05	$81.00
Purchase #5	$171.88	7.850%	$185.3726	$185.37	$185.35	$185.40
Purchase #6	$119.28	7.182%	$127.8467	$127.85	$127.85	$127.80
Purchase #7	$52.90	6.169%	$56.1634	$56.16	$56.15	$56.20
7 purchase totals =	$679.42		$728.1695	$728.16	$728.15	$728.20