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	$77.53	10.454%	$85.635	$85.64	$85.65	$85.60
Purchase #2	$101.46	8.803%	$110.3915	$110.39	$110.40	$110.40
Purchase #3	$35.59	13.841%	$40.516	$40.52	$40.50	$40.50
Purchase #4	$9.34	8.441%	$10.1284	$10.13	$10.15	$10.10
Purchase #5	$248.48	12.661%	$279.9401	$279.94	$279.95	$279.90
Purchase #6	$38.57	5.140%	$40.5525	$40.55	$40.55	$40.60
Purchase #7	$207.76	5.792%	$219.7935	$219.79	$219.80	$219.80
7 purchase totals =	$718.73		$786.9570	$786.96	$787.00	$786.90