The laws in South Africa are different from the laws in the United States (and different from the laws of any one of the states in the US). We cannot give you general advice beyond saying that it's bad to lie and it's likely a crime to lie to the police.
I live in South Africa. The amount is 5000 ZAR which is equivalent to 355 USD. The full scenario of my statement is as follows to the police.
I went to the casino , won a few chips ( about 8000 ZAR, but lost it to about 6500 ZAR and cashed it ) , I took a photo of the chips I had won and cashed it out thereafer. This was several days earlier, but I did come back and have that amount in cash with me in the car the day I was robbed.
Earlier the day I was robbed I was at the casino , but did not win , but went to my car several times to collect cash which I stored inside the car.In my statement I said that I had won it the day I was robbed, but in fact I won it a few days earlier, and it can be confirmed by the casino. There is photo evidence of the chips I won before I cashed it out at the casino, which I sent to a friend on my whatsapp. There should also be footage of me entering and leaving the casino several times going back to my car collecting cash each time(I had a few thousand in notes in my car so that I dont spend it all at once), the day I was robbe. Even if it is possible , the CCTV cameras could catch a glimpse of what was inside the car inside the casino parking lot and a few notes might be spotted.The total amount of cash that was inside the car could not be determined , but I disclosed the amount at 5000. My iphone 7, which new could be valued at 13000 ZAR which can be confirmed by the CCTV cameras inside the casino , was also stolen.The exact amount of cash inside my wallet could be more than 5000 or less but it was around that amount.
I stopped at a Traffic light and a black GTI stopped next to me, 2 men jumped out (one from the passenger seat and one from the back seat).The person in the passenger seat had a gun and held it against my window.I was scared shitless and I really wet myself because of the shock.I opened the car doors because I knew he would shoot me if I tried to resist.The person who jumped out of the backseat grabbed everything he ought to be valuable(backpack, wallet and Iphone)All of this took place in a matter of seconds and I was left completely shell shocked thereafter.I couldn't catch a glimpse of the number plates or the details of their faces.
But pretty useless, since you completely ignored what you were told when you posted originally - that this forum is for US law only, which is very different from the laws in your country. You need to speak with an attorney if you want to have any hope of learning what you need to do.