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	$200.85	12.283%	$225.5204	$225.52	$225.50	$225.50
Purchase #2	$127.81	13.448%	$144.9979	$145.00	$145.00	$145.00
Purchase #3	$167.48	10.819%	$185.5997	$185.60	$185.60	$185.60
Purchase #4	$40.48	7.845%	$43.6557	$43.66	$43.65	$43.70
Purchase #5	$159.53	10.866%	$176.8645	$176.86	$176.85	$176.90
Purchase #6	$182.60	11.269%	$203.1772	$203.18	$203.20	$203.20
Purchase #7	$170.86	9.833%	$187.6607	$187.66	$187.65	$187.70
7 purchase totals =	$1,049.61		$1,167.4761	$1,167.48	$1,167.45	$1,167.60