Karate is usually taught using the original Japanese terms, and that includes counting in Japanese. The second syllable is slightly suppressed, so "Ichi" becomes phonetically more like "itch!" and "Roku" sounds more like "Rokk".
Traditionally, in Kihon (training of basic techniques), students produce a Ki-Ai (Shout) at the 10th repetition of a technique. In partner training such as Ippon Kumite (one-step sparring), the speed and power of each technique is gradually increased, and the 5th repetition (in some Dojos the 3rd) is accompanied by a Ki-Ai at the final technique of both attacker and defender.