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	$230.57	11.680%	$257.5006	$257.50	$257.50	$257.50
Purchase #2	$157.59	10.150%	$173.5854	$173.59	$173.60	$173.60
Purchase #3	$34.80	3.344%	$35.9637	$35.96	$35.95	$36.00
Purchase #4	$209.70	13.767%	$238.5694	$238.57	$238.55	$238.60
Purchase #5	$228.61	5.138%	$240.356	$240.36	$240.35	$240.40
Purchase #6	$108.38	10.219%	$119.4554	$119.46	$119.45	$119.50
Purchase #7	$117.25	12.187%	$131.5393	$131.54	$131.55	$131.50
7 purchase totals =	$1,086.90		$1,196.9698	$1,196.98	$1,196.95	$1,197.10