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	$102.61	10.583%	$113.4692	$113.47	$113.45	$113.50
Purchase #2	$158.66	5.466%	$167.3324	$167.33	$167.35	$167.30
Purchase #3	$11.45	3.542%	$11.8556	$11.86	$11.85	$11.90
Purchase #4	$153.85	6.562%	$163.9456	$163.95	$163.95	$163.90
Purchase #5	$169.88	13.239%	$192.3704	$192.37	$192.35	$192.40
Purchase #6	$167.61	3.543%	$173.5484	$173.55	$173.55	$173.50
Purchase #7	$172.64	13.725%	$196.3348	$196.33	$196.35	$196.30
7 purchase totals =	$936.70		$1,018.8564	$1,018.86	$1,018.85	$1,018.80