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	$162.69	8.752%	$176.9286	$176.93	$176.95	$176.90
Purchase #2	$98.31	10.242%	$108.3789	$108.38	$108.40	$108.40
Purchase #3	$109.89	10.792%	$121.7493	$121.75	$121.75	$121.70
Purchase #4	$12.33	3.593%	$12.773	$12.77	$12.75	$12.80
Purchase #5	$152.97	13.389%	$173.4512	$173.45	$173.45	$173.50
Purchase #6	$65.84	10.439%	$72.713	$72.71	$72.70	$72.70
Purchase #7	$82.94	9.235%	$90.5995	$90.60	$90.60	$90.60
7 purchase totals =	$684.97		$756.5935	$756.59	$756.60	$756.60