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	$10.82	5.822%	$11.4499	$11.45	$11.45	$11.40
Purchase #2	$153.84	6.769%	$164.2534	$164.25	$164.25	$164.30
Purchase #3	$234.85	3.439%	$242.9265	$242.93	$242.95	$242.90
Purchase #4	$155.87	6.496%	$165.9953	$166.00	$166.00	$166.00
Purchase #5	$83.61	9.858%	$91.8523	$91.85	$91.85	$91.90
Purchase #6	$27.31	5.660%	$28.8557	$28.86	$28.85	$28.90
Purchase #7	$129.30	11.837%	$144.6052	$144.61	$144.60	$144.60
7 purchase totals =	$795.60		$849.9383	$849.95	$849.95	$850.00