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	$153.70	7.285%	$164.897	$164.90	$164.90	$164.90
Purchase #2	$82.66	9.639%	$90.6276	$90.63	$90.65	$90.60
Purchase #3	$5.43	3.576%	$5.6242	$5.62	$5.60	$5.60
Purchase #4	$38.87	10.260%	$42.8581	$42.86	$42.85	$42.90
Purchase #5	$131.55	4.592%	$137.5908	$137.59	$137.60	$137.60
Purchase #6	$230.96	11.510%	$257.5435	$257.54	$257.55	$257.50
Purchase #7	$229.72	5.147%	$241.5437	$241.54	$241.55	$241.50
7 purchase totals =	$872.89		$940.6849	$940.68	$940.70	$940.60