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	$118.29	3.192%	$122.0658	$122.07	$122.05	$122.10
Purchase #2	$178.40	6.718%	$190.3849	$190.38	$190.40	$190.40
Purchase #3	$176.52	9.113%	$192.6063	$192.61	$192.60	$192.60
Purchase #4	$144.51	8.349%	$156.5751	$156.58	$156.60	$156.60
Purchase #5	$162.47	9.177%	$177.3799	$177.38	$177.40	$177.40
Purchase #6	$93.62	8.848%	$101.9035	$101.90	$101.90	$101.90
Purchase #7	$36.27	3.794%	$37.6461	$37.65	$37.65	$37.60
7 purchase totals =	$910.08		$978.5616	$978.57	$978.60	$978.60