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	$8.89	4.411%	$9.2821	$9.28	$9.30	$9.30
Purchase #2	$25.95	9.653%	$28.455	$28.46	$28.45	$28.50
Purchase #3	$171.43	6.194%	$182.0484	$182.05	$182.05	$182.00
Purchase #4	$104.79	9.385%	$114.6245	$114.62	$114.60	$114.60
Purchase #5	$151.87	13.857%	$172.9146	$172.91	$172.90	$172.90
Purchase #6	$205.72	4.213%	$214.387	$214.39	$214.40	$214.40
Purchase #7	$83.85	8.328%	$90.833	$90.83	$90.85	$90.80
7 purchase totals =	$752.50		$812.5446	$812.54	$812.55	$812.50