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	$63.97	12.792%	$72.153	$72.15	$72.15	$72.20
Purchase #2	$14.99	3.298%	$15.4844	$15.48	$15.50	$15.50
Purchase #3	$69.92	10.139%	$77.0092	$77.01	$77.00	$77.00
Purchase #4	$153.89	6.706%	$164.2099	$164.21	$164.20	$164.20
Purchase #5	$157.40	10.487%	$173.9065	$173.91	$173.90	$173.90
Purchase #6	$202.93	7.158%	$217.4557	$217.46	$217.45	$217.50
Purchase #7	$44.36	3.540%	$45.9303	$45.93	$45.95	$45.90
7 purchase totals =	$707.46		$766.1490	$766.15	$766.15	$766.20