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	$10.47	10.813%	$11.6021	$11.60	$11.60	$11.60
Purchase #2	$166.88	12.659%	$188.0053	$188.01	$188.00	$188.00
Purchase #3	$81.70	10.774%	$90.5024	$90.50	$90.50	$90.50
Purchase #4	$15.43	4.178%	$16.0747	$16.07	$16.05	$16.10
Purchase #5	$159.58	4.393%	$166.5903	$166.59	$166.60	$166.60
Purchase #6	$145.66	10.428%	$160.8494	$160.85	$160.85	$160.80
Purchase #7	$90.94	13.738%	$103.4333	$103.43	$103.45	$103.40
7 purchase totals =	$670.66		$737.0575	$737.05	$737.05	$737.00