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	$200.93	8.301%	$217.6092	$217.61	$217.60	$217.60
Purchase #2	$34.74	12.189%	$38.9745	$38.97	$38.95	$39.00
Purchase #3	$20.98	3.503%	$21.7149	$21.71	$21.70	$21.70
Purchase #4	$198.94	5.361%	$209.6052	$209.61	$209.60	$209.60
Purchase #5	$98.65	10.802%	$109.3062	$109.31	$109.30	$109.30
Purchase #6	$83.38	4.140%	$86.8319	$86.83	$86.85	$86.80
Purchase #7	$165.39	13.856%	$188.3064	$188.31	$188.30	$188.30
7 purchase totals =	$803.01		$872.3483	$872.35	$872.30	$872.30