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	$19.83	13.184%	$22.4444	$22.44	$22.45	$22.40
Purchase #2	$190.32	11.874%	$212.9186	$212.92	$212.90	$212.90
Purchase #3	$200.95	12.274%	$225.6146	$225.61	$225.60	$225.60
Purchase #4	$206.84	9.145%	$225.7555	$225.76	$225.75	$225.80
Purchase #5	$131.86	9.544%	$144.4447	$144.44	$144.45	$144.40
Purchase #6	$27.34	13.416%	$31.0079	$31.01	$31.00	$31.00
Purchase #7	$166.48	10.737%	$184.355	$184.36	$184.35	$184.40
7 purchase totals =	$943.62		$1,046.5407	$1,046.54	$1,046.50	$1,046.50