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	$119.91	10.546%	$132.5557	$132.56	$132.55	$132.60
Purchase #2	$238.77	10.193%	$263.1078	$263.11	$263.10	$263.10
Purchase #3	$63.59	3.558%	$65.8525	$65.85	$65.85	$65.90
Purchase #4	$22.64	9.189%	$24.7204	$24.72	$24.70	$24.70
Purchase #5	$54.82	13.287%	$62.1039	$62.10	$62.10	$62.10
Purchase #6	$104.60	6.218%	$111.104	$111.10	$111.10	$111.10
Purchase #7	$241.41	7.474%	$259.453	$259.45	$259.45	$259.50
7 purchase totals =	$845.74		$918.8973	$918.89	$918.85	$919.00