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	$78.91	8.622%	$85.7136	$85.71	$85.70	$85.70
Purchase #2	$49.60	13.784%	$56.4369	$56.44	$56.45	$56.40
Purchase #3	$19.90	8.336%	$21.5589	$21.56	$21.55	$21.60
Purchase #4	$10.63	7.858%	$11.4653	$11.47	$11.45	$11.50
Purchase #5	$94.71	9.215%	$103.4375	$103.44	$103.45	$103.40
Purchase #6	$162.34	12.682%	$182.928	$182.93	$182.95	$182.90
Purchase #7	$242.86	7.246%	$260.4576	$260.46	$260.45	$260.50
7 purchase totals =	$658.95		$721.9978	$722.01	$722.00	$722.00