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	$130.37	7.268%	$139.8453	$139.85	$139.85	$139.80
Purchase #2	$97.71	9.679%	$107.1674	$107.17	$107.15	$107.20
Purchase #3	$35.96	4.108%	$37.4372	$37.44	$37.45	$37.40
Purchase #4	$149.54	11.869%	$167.2889	$167.29	$167.30	$167.30
Purchase #5	$131.27	5.233%	$138.1394	$138.14	$138.15	$138.10
Purchase #6	$203.90	11.600%	$227.5524	$227.55	$227.55	$227.60
Purchase #7	$109.29	12.611%	$123.0726	$123.07	$123.05	$123.10
7 purchase totals =	$858.04		$940.5032	$940.51	$940.50	$940.50