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	$226.89	9.105%	$247.5483	$247.55	$247.55	$247.50
Purchase #2	$137.76	4.514%	$143.9785	$143.98	$144.00	$144.00
Purchase #3	$81.93	10.463%	$90.5023	$90.50	$90.50	$90.50
Purchase #4	$21.94	6.826%	$23.4376	$23.44	$23.45	$23.40
Purchase #5	$72.67	13.658%	$82.5953	$82.60	$82.60	$82.60
Purchase #6	$226.91	13.395%	$257.3046	$257.30	$257.30	$257.30
Purchase #7	$175.91	6.479%	$187.3072	$187.31	$187.30	$187.30
7 purchase totals =	$944.01		$1,032.6738	$1,032.68	$1,032.70	$1,032.60