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	$192.78	13.484%	$218.7745	$218.77	$218.75	$218.80
Purchase #2	$151.32	8.825%	$164.674	$164.67	$164.65	$164.70
Purchase #3	$155.43	9.874%	$170.7772	$170.78	$170.80	$170.80
Purchase #4	$53.51	4.672%	$56.01	$56.01	$56.00	$56.00
Purchase #5	$51.40	4.244%	$53.5814	$53.58	$53.60	$53.60
Purchase #6	$200.97	10.241%	$221.5513	$221.55	$221.55	$221.60
Purchase #7	$247.25	3.467%	$255.8222	$255.82	$255.80	$255.80
7 purchase totals =	$1,052.66		$1,141.1906	$1,141.18	$1,141.15	$1,141.30