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	$198.39	7.784%	$213.8327	$213.83	$213.85	$213.80
Purchase #2	$133.29	9.807%	$146.3618	$146.36	$146.35	$146.40
Purchase #3	$82.63	3.139%	$85.2238	$85.22	$85.20	$85.20
Purchase #4	$157.75	6.427%	$167.8886	$167.89	$167.90	$167.90
Purchase #5	$49.86	5.477%	$52.5908	$52.59	$52.60	$52.60
Purchase #6	$38.43	3.176%	$39.6505	$39.65	$39.65	$39.70
Purchase #7	$61.47	8.249%	$66.5407	$66.54	$66.55	$66.50
7 purchase totals =	$721.82		$772.0889	$772.08	$772.10	$772.10