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	$145.66	8.190%	$157.5896	$157.59	$157.60	$157.60
Purchase #2	$6.52	11.847%	$7.2924	$7.29	$7.30	$7.30
Purchase #3	$156.89	12.682%	$176.7868	$176.79	$176.80	$176.80
Purchase #4	$115.94	13.484%	$131.5733	$131.57	$131.55	$131.60
Purchase #5	$168.40	7.200%	$180.5248	$180.52	$180.50	$180.50
Purchase #6	$167.75	5.823%	$177.5181	$177.52	$177.50	$177.50
Purchase #7	$228.31	4.466%	$238.5063	$238.51	$238.50	$238.50
7 purchase totals =	$989.47		$1,069.7913	$1,069.79	$1,069.75	$1,069.80