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	$219.54	5.632%	$231.9045	$231.90	$231.90	$231.90
Purchase #2	$27.52	8.595%	$29.8853	$29.89	$29.90	$29.90
Purchase #3	$114.89	8.761%	$124.9555	$124.96	$124.95	$125.00
Purchase #4	$150.45	9.451%	$164.669	$164.67	$164.65	$164.70
Purchase #5	$123.30	11.411%	$137.3698	$137.37	$137.35	$137.40
Purchase #6	$60.46	10.349%	$66.717	$66.72	$66.70	$66.70
Purchase #7	$126.42	3.144%	$130.3946	$130.39	$130.40	$130.40
7 purchase totals =	$822.58		$885.8957	$885.90	$885.85	$886.00