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	$80.25	12.477%	$90.2628	$90.26	$90.25	$90.30
Purchase #2	$222.85	6.330%	$236.9564	$236.96	$236.95	$237.00
Purchase #3	$128.94	12.156%	$144.6139	$144.61	$144.60	$144.60
Purchase #4	$214.30	7.625%	$230.6404	$230.64	$230.65	$230.60
Purchase #5	$117.57	8.553%	$127.6258	$127.63	$127.65	$127.60
Purchase #6	$101.93	10.189%	$112.3156	$112.32	$112.30	$112.30
Purchase #7	$219.56	3.206%	$226.5991	$226.60	$226.60	$226.60
7 purchase totals =	$1,085.40		$1,169.0140	$1,169.02	$1,169.00	$1,169.00