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	$188.80	10.649%	$208.9053	$208.91	$208.90	$208.90
Purchase #2	$55.25	13.560%	$62.7419	$62.74	$62.75	$62.70
Purchase #3	$228.84	5.577%	$241.6024	$241.60	$241.60	$241.60
Purchase #4	$164.49	5.230%	$173.0928	$173.09	$173.10	$173.10
Purchase #5	$93.88	7.466%	$100.8891	$100.89	$100.90	$100.90
Purchase #6	$113.64	5.309%	$119.6731	$119.67	$119.65	$119.70
Purchase #7	$176.28	9.385%	$192.8239	$192.82	$192.80	$192.80
7 purchase totals =	$1,021.18		$1,099.7285	$1,099.72	$1,099.70	$1,099.70