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	$118.39	4.597%	$123.8324	$123.83	$123.85	$123.80
Purchase #2	$29.96	5.434%	$31.588	$31.59	$31.60	$31.60
Purchase #3	$27.44	8.513%	$29.776	$29.78	$29.80	$29.80
Purchase #4	$137.77	6.619%	$146.889	$146.89	$146.90	$146.90
Purchase #5	$145.65	3.561%	$150.8366	$150.84	$150.85	$150.80
Purchase #6	$36.96	9.835%	$40.595	$40.60	$40.60	$40.60
Purchase #7	$82.55	4.299%	$86.0988	$86.10	$86.10	$86.10
7 purchase totals =	$578.72		$609.6158	$609.63	$609.70	$609.60