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	$150.64	11.475%	$167.9259	$167.93	$167.95	$167.90
Purchase #2	$73.98	6.228%	$78.5875	$78.59	$78.60	$78.60
Purchase #3	$102.93	4.189%	$107.2417	$107.24	$107.25	$107.20
Purchase #4	$54.92	12.617%	$61.8493	$61.85	$61.85	$61.80
Purchase #5	$96.25	9.452%	$105.3476	$105.35	$105.35	$105.30
Purchase #6	$217.40	8.602%	$236.1007	$236.10	$236.10	$236.10
Purchase #7	$157.69	4.247%	$164.3871	$164.39	$164.40	$164.40
7 purchase totals =	$853.81		$921.4398	$921.45	$921.50	$921.30