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	$50.90	12.382%	$57.2024	$57.20	$57.20	$57.20
Purchase #2	$117.87	4.484%	$123.1553	$123.16	$123.15	$123.20
Purchase #3	$158.88	12.453%	$178.6653	$178.67	$178.65	$178.70
Purchase #4	$134.81	5.593%	$142.3499	$142.35	$142.35	$142.30
Purchase #5	$212.56	3.384%	$219.753	$219.75	$219.75	$219.80
Purchase #6	$157.53	9.226%	$172.0637	$172.06	$172.05	$172.10
Purchase #7	$107.79	3.524%	$111.5885	$111.59	$111.60	$111.60
7 purchase totals =	$940.34		$1,004.7781	$1,004.78	$1,004.75	$1,004.90