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	$212.29	5.739%	$224.4733	$224.47	$224.45	$224.50
Purchase #2	$66.80	13.791%	$76.0124	$76.01	$76.00	$76.00
Purchase #3	$29.94	3.762%	$31.0663	$31.07	$31.05	$31.10
Purchase #4	$112.42	9.531%	$123.1348	$123.13	$123.15	$123.10
Purchase #5	$164.46	5.411%	$173.3589	$173.36	$173.35	$173.40
Purchase #6	$36.66	4.119%	$38.17	$38.17	$38.15	$38.20
Purchase #7	$42.49	3.382%	$43.927	$43.93	$43.95	$43.90
7 purchase totals =	$665.06		$710.1427	$710.14	$710.10	$710.20