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	$118.59	4.405%	$123.8139	$123.81	$123.80	$123.80
Purchase #2	$248.39	9.648%	$272.3547	$272.35	$272.35	$272.40
Purchase #3	$202.59	11.153%	$225.1849	$225.18	$225.20	$225.20
Purchase #4	$49.92	9.116%	$54.4707	$54.47	$54.45	$54.50
Purchase #5	$132.72	5.271%	$139.7157	$139.72	$139.70	$139.70
Purchase #6	$30.70	12.649%	$34.5832	$34.58	$34.60	$34.60
Purchase #7	$194.73	5.502%	$205.444	$205.44	$205.45	$205.40
7 purchase totals =	$977.64		$1,055.5671	$1,055.55	$1,055.55	$1,055.60