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	$151.60	4.498%	$158.419	$158.42	$158.40	$158.40
Purchase #2	$10.67	13.439%	$12.1039	$12.10	$12.10	$12.10
Purchase #3	$83.33	8.819%	$90.6789	$90.68	$90.70	$90.70
Purchase #4	$156.90	12.835%	$177.0381	$177.04	$177.05	$177.00
Purchase #5	$41.41	9.772%	$45.4566	$45.46	$45.45	$45.50
Purchase #6	$167.43	5.469%	$176.5867	$176.59	$176.60	$176.60
Purchase #7	$225.80	12.184%	$253.3115	$253.31	$253.30	$253.30
7 purchase totals =	$837.14		$913.5947	$913.60	$913.60	$913.60