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	$119.85	3.123%	$123.5929	$123.59	$123.60	$123.60
Purchase #2	$71.54	4.145%	$74.5053	$74.51	$74.50	$74.50
Purchase #3	$177.26	3.150%	$182.8437	$182.84	$182.85	$182.80
Purchase #4	$196.90	5.697%	$208.1174	$208.12	$208.10	$208.10
Purchase #5	$143.56	13.500%	$162.9406	$162.94	$162.95	$162.90
Purchase #6	$148.78	5.579%	$157.0804	$157.08	$157.10	$157.10
Purchase #7	$33.70	12.622%	$37.9536	$37.95	$37.95	$38.00
7 purchase totals =	$891.59		$947.0339	$947.03	$947.05	$947.00