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	$188.30	10.692%	$208.433	$208.43	$208.45	$208.40
Purchase #2	$83.59	11.782%	$93.4386	$93.44	$93.45	$93.40
Purchase #3	$13.35	4.784%	$13.9887	$13.99	$14.00	$14.00
Purchase #4	$99.84	5.256%	$105.0876	$105.09	$105.10	$105.10
Purchase #5	$224.92	5.310%	$236.8633	$236.86	$236.85	$236.90
Purchase #6	$81.28	11.691%	$90.7824	$90.78	$90.80	$90.80
Purchase #7	$224.39	6.464%	$238.8946	$238.89	$238.90	$238.90
7 purchase totals =	$915.67		$987.4882	$987.48	$987.55	$987.50