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	$36.27	9.738%	$39.802	$39.80	$39.80	$39.80
Purchase #2	$70.88	8.738%	$77.0735	$77.07	$77.05	$77.10
Purchase #3	$202.82	11.112%	$225.3574	$225.36	$225.35	$225.40
Purchase #4	$55.94	11.801%	$62.5415	$62.54	$62.55	$62.50
Purchase #5	$213.27	6.636%	$227.4226	$227.42	$227.40	$227.40
Purchase #6	$186.26	7.134%	$199.5478	$199.55	$199.55	$199.50
Purchase #7	$141.48	3.588%	$146.5563	$146.56	$146.55	$146.60
7 purchase totals =	$906.92		$978.3011	$978.30	$978.25	$978.30