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	$199.48	10.175%	$219.7771	$219.78	$219.80	$219.80
Purchase #2	$94.90	13.239%	$107.4638	$107.46	$107.45	$107.50
Purchase #3	$10.55	3.813%	$10.9523	$10.95	$10.95	$11.00
Purchase #4	$39.25	10.695%	$43.4478	$43.45	$43.45	$43.40
Purchase #5	$139.45	10.214%	$153.6934	$153.69	$153.70	$153.70
Purchase #6	$81.64	9.477%	$89.377	$89.38	$89.40	$89.40
Purchase #7	$7.81	4.324%	$8.1477	$8.15	$8.15	$8.10
7 purchase totals =	$573.08		$632.8591	$632.86	$632.90	$632.90