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	$127.61	9.663%	$139.941	$139.94	$139.95	$139.90
Purchase #2	$173.33	5.356%	$182.6136	$182.61	$182.60	$182.60
Purchase #3	$215.84	10.659%	$238.8464	$238.85	$238.85	$238.80
Purchase #4	$117.46	5.123%	$123.4775	$123.48	$123.50	$123.50
Purchase #5	$59.76	3.752%	$62.0022	$62.00	$62.00	$62.00
Purchase #6	$221.46	4.294%	$230.9695	$230.97	$230.95	$231.00
Purchase #7	$146.64	10.619%	$162.2117	$162.21	$162.20	$162.20
7 purchase totals =	$1,062.10		$1,140.0619	$1,140.06	$1,140.05	$1,140.00