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	$173.41	5.323%	$182.6406	$182.64	$182.65	$182.60
Purchase #2	$29.49	11.329%	$32.8309	$32.83	$32.85	$32.80
Purchase #3	$137.87	9.268%	$150.6478	$150.65	$150.65	$150.60
Purchase #4	$95.58	7.679%	$102.9196	$102.92	$102.90	$102.90
Purchase #5	$144.39	6.180%	$153.3133	$153.31	$153.30	$153.30
Purchase #6	$63.37	5.451%	$66.8243	$66.82	$66.80	$66.80
Purchase #7	$61.96	8.622%	$67.3022	$67.30	$67.30	$67.30
7 purchase totals =	$706.07		$756.4787	$756.47	$756.45	$756.30