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	$140.26	3.126%	$144.6445	$144.64	$144.65	$144.60
Purchase #2	$132.60	13.254%	$150.1748	$150.17	$150.15	$150.20
Purchase #3	$43.47	8.509%	$47.1689	$47.17	$47.15	$47.20
Purchase #4	$86.92	4.538%	$90.8644	$90.86	$90.85	$90.90
Purchase #5	$181.30	10.853%	$200.9765	$200.98	$201.00	$201.00
Purchase #6	$116.53	5.139%	$122.5185	$122.52	$122.50	$122.50
Purchase #7	$138.73	3.162%	$143.1166	$143.12	$143.10	$143.10
7 purchase totals =	$839.81		$899.4642	$899.46	$899.40	$899.50