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	$111.63	10.375%	$123.2116	$123.21	$123.20	$123.20
Purchase #2	$246.30	9.345%	$269.3167	$269.32	$269.30	$269.30
Purchase #3	$22.75	12.411%	$25.5735	$25.57	$25.55	$25.60
Purchase #4	$29.67	13.273%	$33.6081	$33.61	$33.60	$33.60
Purchase #5	$236.42	8.632%	$256.8278	$256.83	$256.85	$256.80
Purchase #6	$158.84	11.340%	$176.8525	$176.85	$176.85	$176.90
Purchase #7	$46.34	3.202%	$47.8238	$47.82	$47.80	$47.80
7 purchase totals =	$851.95		$933.2140	$933.21	$933.15	$933.20