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	$219.76	8.415%	$238.2528	$238.25	$238.25	$238.30
Purchase #2	$226.83	13.239%	$256.86	$256.86	$256.85	$256.90
Purchase #3	$81.82	5.786%	$86.5541	$86.55	$86.55	$86.60
Purchase #4	$134.28	6.147%	$142.5342	$142.53	$142.55	$142.50
Purchase #5	$128.85	9.192%	$140.6939	$140.69	$140.70	$140.70
Purchase #6	$240.78	3.247%	$248.5981	$248.60	$248.60	$248.60
Purchase #7	$217.75	6.516%	$231.9386	$231.94	$231.95	$231.90
7 purchase totals =	$1,250.07		$1,345.4317	$1,345.42	$1,345.45	$1,345.50