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	$126.28	10.663%	$139.7452	$139.75	$139.75	$139.70
Purchase #2	$208.59	12.724%	$235.131	$235.13	$235.15	$235.10
Purchase #3	$93.58	5.690%	$98.9047	$98.90	$98.90	$98.90
Purchase #4	$121.83	10.582%	$134.7221	$134.72	$134.70	$134.70
Purchase #5	$182.32	10.184%	$200.8875	$200.89	$200.90	$200.90
Purchase #6	$127.36	13.604%	$144.6861	$144.69	$144.70	$144.70
Purchase #7	$183.45	9.493%	$200.8649	$200.86	$200.85	$200.90
7 purchase totals =	$1,043.41		$1,154.9415	$1,154.94	$1,154.95	$1,154.90