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	$242.47	9.688%	$265.9605	$265.96	$265.95	$266.00
Purchase #2	$156.41	4.713%	$163.7816	$163.78	$163.80	$163.80
Purchase #3	$21.72	3.181%	$22.4109	$22.41	$22.40	$22.40
Purchase #4	$41.54	4.297%	$43.325	$43.33	$43.35	$43.30
Purchase #5	$151.86	13.680%	$172.6344	$172.63	$172.65	$172.60
Purchase #6	$86.82	10.383%	$95.8345	$95.83	$95.85	$95.80
Purchase #7	$157.56	7.833%	$169.9017	$169.90	$169.90	$169.90
7 purchase totals =	$858.38		$933.8486	$933.84	$933.90	$933.80