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	$77.78	12.311%	$87.3555	$87.36	$87.35	$87.40
Purchase #2	$11.39	7.591%	$12.2546	$12.25	$12.25	$12.30
Purchase #3	$171.74	4.181%	$178.9204	$178.92	$178.90	$178.90
Purchase #4	$66.32	8.613%	$72.0321	$72.03	$72.05	$72.00
Purchase #5	$37.78	12.289%	$42.4228	$42.42	$42.40	$42.40
Purchase #6	$47.95	10.236%	$52.8582	$52.86	$52.85	$52.90
Purchase #7	$176.40	5.866%	$186.7476	$186.75	$186.75	$186.70
7 purchase totals =	$589.36		$632.5912	$632.59	$632.55	$632.60