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	$38.79	4.617%	$40.5809	$40.58	$40.60	$40.60
Purchase #2	$132.82	6.326%	$141.2222	$141.22	$141.20	$141.20
Purchase #3	$7.58	4.337%	$7.9087	$7.91	$7.90	$7.90
Purchase #4	$164.32	12.413%	$184.717	$184.72	$184.70	$184.70
Purchase #5	$92.84	6.149%	$98.5487	$98.55	$98.55	$98.50
Purchase #6	$50.50	4.393%	$52.7185	$52.72	$52.70	$52.70
Purchase #7	$220.52	4.464%	$230.364	$230.36	$230.35	$230.40
7 purchase totals =	$707.37		$756.0600	$756.06	$756.00	$756.00