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	$102.53	8.567%	$111.3137	$111.31	$111.30	$111.30
Purchase #2	$139.39	7.653%	$150.0575	$150.06	$150.05	$150.10
Purchase #3	$98.86	12.287%	$111.0069	$111.01	$111.00	$111.00
Purchase #4	$238.33	3.243%	$246.059	$246.06	$246.05	$246.10
Purchase #5	$180.28	3.772%	$187.0802	$187.08	$187.10	$187.10
Purchase #6	$212.39	6.719%	$226.6605	$226.66	$226.65	$226.70
Purchase #7	$203.50	11.757%	$227.4255	$227.43	$227.45	$227.40
7 purchase totals =	$1,175.28		$1,259.6033	$1,259.61	$1,259.60	$1,259.70